Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/eftf/ifcs57587.2023.10272086

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Publishing type：Research paper (scientific journal)   Publisher：Optica Publishing Group  

The application of silicon photomultiplier (SiPM) technology for weak-light detection at a single photon level has expanded thanks to its better photon detection efficiency in comparison to a conventional photomultiplier tube (PMT). SiPMs with large detection area have recently become commercially available, enabling applications where the photon flux is low both temporarily and spatially. On the other hand, several drawbacks exist in the usage of SiPMs such as a higher dark count rate, many readout channels, slow response time, and optical crosstalk; therefore, users need to carefully consider the trade-offs. This work presents a SiPM-embedded compact large-area photon detection module. Various techniques are adopted to overcome the disadvantages of SiPMs so that it can be generally utilized as an upgrade from a PMT. A simple cooling component and recently developed optical crosstalk suppression method are adopted to reduce the noise which is more serious for larger-area SiPMs. A dedicated readout circuit increases the response frequency and reduces the number of readout channels. We favorably compare this design with a conventional PMT and obtain both higher photon detection efficiency and larger-area acceptance.

DOI： 10.1364/oe.475109

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Other Link： https://opg.optica.org/viewmedia.cfm?URI=oe-31-2-1943&seq=0

Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

Synchrotron-radiation based Mössbauer spectroscopy has become a useful technique capable for investigating various Mössbauer isotopes. For a typical experimental setup, the information associated with the pulse height (that is, energy) in an avalanche photodiode (APD) detector has not been used effectively. By using a system for simultaneous measurement system of time and energy associated with the APD signal, a system for the time- and energy-resolved Mössbauer spectroscopy has been developed. In this system, the pulse height information was converted to the time information through an amplitude-to-time converter applied to one of the divided signals from the APD. The corresponding time information was processed separately from another one of the divided signals. Both signals are recorded by a multi-channel scaler in an event-by-event data acquisition process. The velocity information from the Mössbauer transducer was also recorded as a tag for each signal event. Thus, the Mössbauer spectra with any time- and energy-window can be reconstructed after the data collection process. This system can be used for many purposes in time- and energy-resolved Mössbauer spectroscopy, and shows significant promise for use with other fast detectors and for various types of experiments.

DOI： 10.1088/1742-6596/2380/1/012136

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Other Link： https://iopscience.iop.org/article/10.1088/1742-6596/2380/1/012136/pdf

Publishing type：Research paper (scientific journal)   Publisher：EDP Sciences  

A new hyperon-proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the Σ⁺p, Σ⁻p elastic scatterings and the Σ⁻p → Λn scattering by identifying a lot of Σ particles in the momentum ranging from 0.4 to 0.8 GeV/c produced by the π^±p → K⁺Σ^± reactions. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions. Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized Λ beam for providing quantitative information on the ΛN interaction. The results of three Σp channels and future prospects of the Λp scattering experiment are described.

DOI： 10.1051/epjconf/202227104001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.nima.2022.167513

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Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

We performed a novel Σ+p scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 Σ+p elastic scattering events were identified from 4.9 × 107 tagged Σ+ particles in the Σ+ momentum range 0.44–0.80 GeV/c. The differential cross sections of the Σ+p elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the 3S1 and 1P1 channels for the first time. The phase shift of the 3S1 channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated as $20^\circ \lt |\delta _{^3S_1}|\lt 35^\circ$. If the sign of $\delta _{^3S_1}$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.

DOI： 10.1093/ptep/ptac101

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Publishing type：Research paper (scientific journal)  

The differential cross sections of the ς-p→Λn reaction were measured accurately for the ς- momentum (pς) ranging from 470 to 650 MeV/c at the J-PARC Hadron Experimental Facility. Precise angular information about the ς-p→Λn reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of Δcosθ=0.1. The obtained differential cross sections show a slightly forward-peaking structure in the measured momentum regions. The cross sections integrated for -0.7≤cosθ≤1.0 were obtained as 22.5±0.68 [statistical error(stat.)] ±0.65 [systematic error(syst.)] mb and 15.8±0.83(stat)±0.52(syst) mb for 470<pς(MeV/c)<550 and 550<pς(MeV/c)<650, respectively. These results show a drastic improvement compared with past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.

DOI： 10.1103/PhysRevLett.128.072501

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PubMed

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Publishing type：Research paper (scientific journal)  

A high statistics scattering experiment is performed at the J-PARC Hadron Experimental Facility. Momentum-tagged running in a liquid hydrogen target are accumulated by detecting the reaction with a high intensity beam of 20 M/spill. The differential cross sections of the elastic scattering were derived with a drastically improved accuracy by identifying approximately 4500 events from . The derived differential cross section shows a clear forward-peaking angular distribution for a momentum range from 470 to 850 . The accurate data will impose a strong constraint on the theoretical models of the baryon-baryon interactions.

DOI： 10.1103/PhysRevC.104.045204

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Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevc.104.024306

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.104.024306/fulltext

Publishing type：Research paper (scientific journal)   Publisher：The Optical Society  

DOI： 10.1364/oe.424460

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Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.33.011125

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Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.33.011134

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Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.33.011133

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Publishing type：Research paper (scientific journal)   Publisher：International Union of Crystallography (IUCr)  

This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid <italic>in situ</italic> measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.

DOI： 10.1107/s1600577520014526

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PubMed

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Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

A high statistics ∑p scattering experiment has been performed at the K1.8 beamline in the J-PARC Hadron Experimental Facility. Data for momentum-tagged ∑⁻ beam running in a liquid hydrogen target were accumulated by detecting the ${\pi }_{}^{-}p\to {K}_{}^{+}{\sum }_{}^{-}$ reaction with a high intensity π⁻ beam of 20 M/spill. The number of the Σ⁻ beam was about 1.7 × 10⁷ in total. The ∑⁻ρ elastic scattering and the ∑⁻p → Λn inelastic scattering events were successfully observed with about 100 times larger statistics than that in past experiments.

DOI： 10.1088/1742-6596/1643/1/012174

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Other Link： https://iopscience.iop.org/article/10.1088/1742-6596/1643/1/012174

Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.27.011008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We developed a measurement system that enables the reconstruction of gamma-ray time spectra in cascade decay schemes with 0.3 ns time resolution, which is sufficient for nuclear decay with more than nanoseconds half-life. As this system records all the time and energy information of gamma-rays, the energy regions for the gamma-ray identification can be optimized after the measurement. Moreover, this system has five timing inputs and thus we can record the timing data of external perturbations; we can investigate the responses to the perturbation afterward. This property fulfills the demands required for quantum information research with gamma-rays. (C) 2019 The Japan Society of Applied Physics

DOI： 10.7567/1347-4065/ab3f19

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arXiv

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Other Link： http://arxiv.org/pdf/1905.11029v1

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41586-019-1542-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Thorium-229 is a unique case in nuclear physics: it presents a metastable
first excited state Th-229m, just a few electronvolts above the nuclear ground
state. This so-called isomer is accessible by VUV lasers, which allows
transferring the amazing precision of atomic laser spectroscopy to nuclear
physics. Being able to manipulate the Th-229 nuclear states at will opens up a
multitude of prospects, from studies of the fundamental interactions in physics
to applications as a compact and robust nuclear clock. However, direct optical
excitation of the isomer or its radiative decay back to the ground state has
not yet been observed, and a series of key nuclear structure parameters such as
the exact energies and half-lives of the low-lying nuclear levels of Th-229 are
yet unknown. Here we present the first active optical pumping into Th-229m. Our
scheme employs narrow-band 29 keV synchrotron radiation to resonantly excite
the second excited state, which then predominantly decays into the isomer. We
determine the resonance energy with 0.07 eV accuracy, measure a half-life of
82.2 ps, an excitation linewidth of 1.70 neV, and extract the branching ratio
of the second excited state into the ground and isomeric state respectively.
These measurements allow us to re-evaluate gamma spectroscopy data that have
been collected over 40~years.

DOI： 10.1038/s41586-019-1542-3

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arXiv

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Other Link： http://arxiv.org/pdf/1902.04823v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We observed two-photon emission (TPE) signal from the first vibrationally excited state of parahydrogen gas coherently excited by counter-propagating laser pulses. A single narrow-linewidth laser source has roles in the excitation of the parahydrogen molecules and the induction of the TPE process. We measured dependences of the signal energy on the detuning, target gas pressure, and input pulse energies. These results are qualitatively consistent with those obtained by numerical simulations based on Maxwell-Bloch equations with one spatial dimension and one temporal dimension. This study of the TPE process in the counterpropagating injection scheme is an important step toward neutrino mass spectroscopy.

DOI： 10.1088/1361-6455/aafbd0

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arXiv

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Other Link： http://arxiv.org/pdf/1806.04005v2

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This paper reports on the demonstration of a high-rate energy measurement technique using a thin depletion layer silicon avalanche photodiode (Si-APD). A dedicated amplitude-to-time converter is developed to realize simultaneous energy and timing measurement in a high rate condition. The energy response of the system is systematically studied by using monochromatic X-ray beam with an incident energy ranging from 6 to 33 keV. The obtained energy spectra contain clear peaks and tail distributions. The peak fraction monotonously decreases as the incident photon energy increases. This phenomenon can be explained by considering the distribution of the energy deposit in silicon, which is investigated by using a Monte Carlo simulation.

DOI： 10.1016/j.nima.2018.10.029

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The Sigma p scattering experiment has just been started at J-PARC this year (2018). We made "Sigma beam factory" a reality where a beam with an intensity of more than 5x10(5) Sigma(-) beam per day could be produced by using 20 M/spill pi(-) beam. The CATCH system, which is a dedicated system to detect recoil proton from the Sigma p scattering, operated stably under the high counting rate, and its successful operation was confirmed by identifying the pp scattering events in J-PARC. In the June beam time, the production run of the Sigma(-)p scattering was carried out for 2 days, which was just 10% of the requested beam time. The remaining beam time of the Sigma(-)p channel and the Sigma(+)p channel will take place in the spring of 2019.

DOI： 10.1063/1.5118374

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Sissa Medialab Srl  

High-precision measurements of the cosmic-ray antiproton spectrum and sensitive search for cosmological antihelium have been published using the data from BESS-Polar II (Balloon-borne Experiment with a Superconducting Spectrometer) flight in 2007/2008 for a core study of the early Universe using elementary particle measurements. The most sensitive antideuteron search reported used the data obtained by BESS97, BESS98, BESS99, and BESS00, which include the solar minimum period in 1997. We performed a search for antideuterons with unprecedented sensitivity using BESS-Polar II data that is more than ten times the statistics of BESS97 in near solar minimum conditions. The search for antideuteron probes possible exotic sources, such as dark-matter candidates.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer New York LLC  

An appealing candidate of the galactic dark matter is the axion, which was postulated to solve the strong CP (Charge-conjugation Parity) violation problem in the standard particle theory. A new experimental method is proposed to determine the axion mass. The method uses collectively and coherently excited atoms or molecules, the trigger laser inducing galactic axion absorption along with signal photon emission to be detected.

DOI： 10.1140/epjc/s10052-018-6412-x

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Language：English   Publisher：IOP PUBLISHING LTD  

We study nearly degenerate four-wave mixing using a two-photon-allowed
vibrational transition of parahydrogen. A signal photon is generated by a
trigger photon and coherence among parahydrogen, which is prepared by two
counterpropagating pump pulses. The dependence of the signal pulse energy on
the trigger frequency are investigated. The measured spectra vary depending on
the geometry. They shift depending on the direction of the signal pulse and on
the small angle formed by the counterpropagating pump pulses. Furthermore, the
dependence of signal pulse energy on the incident time of the trigger pulse is
investigated. The measured signal pulse energy is high if the trigger pulse is
slightly delayed with respect to the pump pulses. We demonstrate that these
geometry-dependent spectra and coherent-transient response can be explained by
using simple models.

DOI： 10.1088/1361-6455/ab4a6e

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arXiv

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Other Link： http://arxiv.org/pdf/1810.13120v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory's (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest in assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.

DOI： 10.1103/PhysRevAccelBeams.21.053001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Nuclear resonant excitation and detection of its decay signal for the 26.27-keV level of Hg-201 is demonstrated with high-brilliance synchrotron radiation (SR) and a fast x-ray detector system. This SR-based photonuclear excitation scheme, known as nuclear resonant scattering (NRS) in the field of materials science, is also useful for investigating nuclear properties, such as the half-lives and radiative widths of excited nuclear levels. To date, because of the limited time response of the x-ray detector, the nuclear levels to which this method could be applied have been limited to the one whose half-lives are longer than similar to 1 ns. The faster time response of the NRS measurement makes possible NRS experiments on nuclear levels with much shorter half-lives. We have fabricated an x-ray detector system that has a time resolution of 56 ps and a shorter tail function than that reported previously. With the implemented detector system, the NRS signal of the 26.27-keVstate of Hg-201 could be clearly discriminated from the electronic scattering signal at an elapsed time of 1 ns after the SR pulse. The half-life of the state was determined as 629 +/- 18 ps, which has better precision by a factor of three compared with that reported to date obtained from nuclear decay spectroscopy.

DOI： 10.1103/PhysRevC.97.024607

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We report the coherent excitation of the vibrational state of hydrogen molecules by two-photon absorption and the resultant third-harmonic generation (THG). Parahydrogen molecules cooled by liquid nitrogen are irradiated by mid-infrared nanosecond pulses at 4.8 mu m with a nearly Fourier-transform-limited linewidth. The first excited vibrational state of parahydrogen is populated by two-photon absorption of the mid-infrared photons. Because of the narrow linewidth of the mid-infrared pulses, coherence between the ground and excited states is sufficient to induce higher-order processes. Near-infrared photons from the THG are observed at 1.6 mu m. The dependence of the intensity of the near-infrared radiation on mid-infrared pulse energy, target pressure, and cell length is determined. We used a simple formula for THG with consideration of realistic experimental conditions to explain the observed results.

DOI： 10.1088/1361-6455/aa9782

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We investigate how the efficiency of coherently amplified two-photon emission depends on the frequency of one of the two emitted photons, namely the signal photon. This is done over the wavelength range of 5.048-10.21 mu m by using the vibrational transition of parahydrogen. The efficiency increases with the frequency of the signal photon. Considering experimental errors, our results are consistent with the theoretical prediction for the present experimental conditions. This study is an experimental demonstration of the frequency dependence of coherently amplified two-photon emission, and also presents its potential as a light source.

DOI： 10.1103/PhysRevA.96.063827

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We propose a new scheme of producing an intense neutron beam whose yields may exceed those of the existing facilities by a few to several orders of magnitude in the sub-eV region. This scheme employs a MeV gamma beam extracted from circulating quantum ions, which has been recently proposed. The gamma beam is directed to a deuteron target and the photo-disintegration process generates a neutron beam. The calculated neutron energy spectrum is nearly flat down to the neV range, and thus there exists a possibility to utilize a good quality of neutrons especially in sub-eV energy region without using a moderator.

DOI： 10.1142/S0218301317500768

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Scopus

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Other Link： http://orcid.org/0000-0001-8122-5145

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The balloon-borne experiment with a superconducting spectrometer (BESS) instrument was developed as a high-resolution, high-geometric-acceptance magnetic-rigidity spectrometer for sensitive measurements of cosmic-ray antiparticles, searches for antinuclei, and precise measurements of the absolute fluxes of light GCR elements and isotopes. The original BESS experiment flew 8 times over Lynn Lake, Canada and once from Fort Sumner, USA during the period of 1993 through 2002, with continuous improvement in the instrument. Based on the instrument concept inherited from the BESS spectrometer, a very low instrumental energy cutoff for antiprotons was achieved with a new thin-walled superconducting magnet and removal of the outer pressure vessel for BESS-Polar project. The first and second scientific flights called BESS-Polar I/II were successfully performed, over Antarctica in 2004 December and 2007 December respectively. We report the scientific results, focusing on the long-duration flights of BESS-Polar I (2004) and BESS-Polar II (2007-2008). (C) 2017 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2016.11.004

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Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.17.041002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We developed a fast X-ray detector system for nuclear resonant scattering (NRS) experiments. Our system employs silicon avalanche photo-diode (Si-APD) as a fast X-ray sensor. The system is able to acquire both timing and energy of a single X-ray photon simultaneously in a high rate condition, 106 counts per second for one Si-APD. The performance of the system was investigated in SPring-8, a synchrotron radiation facility in Japan. Good time resolution of 120 ps (FWHM) was achieved with a slight tail distribution in the time spectrum by a level of 10(-9) at 1 ns apart from the peak. Using this system, we successfully observed the NRS from the 26.27-keV level of mercury-201, which has a half-life of 630(50) ps. We also demonstrated the reduction of background events caused by radioactive decays in a radioactive sample by discriminating photon energy. Published by AIP Publishing.

DOI： 10.1063/1.4989405

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Sissa Medialab Srl  

A precise knowledge of cosmic-ray hydrogen and helium isotopes provides important information to better understand Galactic cosmic-ray propagation. Deuteron and helium 3 species are mainly secondary particles created by the spallation of primary proton and helium 4 particles during their propagation in the Galaxy. Secondary-to-primary ratios thus bring direct information on the average amount of material traversed by cosmic rays in the interstellar medium. The Balloon-borne Experiment with Superconducting Spectrometer BESS-Polar II flew over Antarctica for 24.5 days from December 2007 through January 2008, during the 23rd solar cycle minimum. The instrument is made of complementary particle detectors which allow to precisely measure the charge, velocity and rigidity of incident cosmic rays. It can accurately separate and precisely measure cosmic-ray hydrogen and helium isotopes between 0.2 and 1.5 GeV/nucleon. These data, which are the most precise to date, will be reported and their implications will be discussed.

DOI： 10.22323/1.301.0210

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Sissa Medialab Srl  

The energy spectra of cosmic-ray antiprotons and protons near solar minimum were precisely measured with BESS-Polar II (Balloon-borne Experiment with a Superconducting Spectrometer) during a long-duration flight over Antarctica in December 2007 and January 2008. The upper-TOF (UTOF) and lower-TOF (LTOF) scintillator hodoscopes measure the charge and velocity of incident particles. A thin plastic scintillator middle-TOF (MTOF) hodoscope is installed on the lower surface of the magnet bore to measure low-energy particles that cannot reach the LTOF. The MTOF further lowers the threshold energy to about 120 MeV for antiproton or proton measurements. We report absolute spectra of the cosmic-ray antiproton in the range 0.12 to 0.4 GeV and the antiproton/proton ratio calculated with UTOF-MTOF trigger events. These new results are independent of the UTOF-LTOF triggered antiproton spectrum published in 2012 and proton spectrum published in 2016.

DOI： 10.22323/1.301.0174

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report observation of two-photon emission from coherently excited
vibrational state of solid parahydrogen, known as one of quantum solids. The
coherent state between the ground and the excited states is prepared by
stimulated Raman scattering using two visible laser pulses. The two-photon
emission is triggered by another mid-infrared laser pulse. The observed
two-photon emission persists even when the trigger pulse is injected long after
the excitation. The observed phenomenon is due to a long decoherence time of
the vibrational states of solid parahydrogen, which is attributed to special
nature as quantum solid. Dependence of the decoherence on target temperature
and residual orthohydrogen concentration are studied along with its time
evolution. It is found that the emission intensity increases even after the
excitation pulses pass through the target completely. The coherence development
is highly suppressed at high target temperature and high residual orthohydrogen
concentration. Effects of target annealing and laser-induced damage on the
target are also observed.

DOI： 10.1021/acs.jpca.7b02011

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arXiv

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Other Link： http://arxiv.org/pdf/1612.05600v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The BESS-Polar Collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over Antarctica in 2004 December and 2007 December at substantially different levels of solar modulation. Proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160 GeV and helium nuclei in the range 0.15-80 GeV/nucleon. The corresponding magnetic-rigidity ranges are 0.6-160 GV for protons and 1.1-160 GV for helium. These spectra are compared to measurements from previous BESS flights and from ATIC-2, PAMELA, and AMS-02. We also report the ratio of the proton and helium fluxes from 1.1 to 160 GV and compare this to the ratios from PAMELA and AMS-02.

DOI： 10.3847/0004-637X/822/2/65

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Language：English   Publisher：ELSEVIER  

Recent years have seen increased theoretical and experimental effort towards the first ever detection of cosmic-ray antideuterons, in particular as an indirect signature of dark matter annihilation or decay. In contrast to indirect dark matter searches using positrons, antiprotons, or gamma-rays, which suffer from relatively high and uncertain astrophysical backgrounds, searches with antideuterons benefit from very suppressed conventional backgrounds, offering a potential breakthrough in unexplored phase space for dark matter. This article is based on the first dedicated cosmic-ray antideuteron workshop, which was held at UCLA in June 2014. It reviews broad classes of dark matter candidates that result in detectable cosmic-ray antideuteron fluxes, as well as the status and prospects of cur rent experimental searches. The coalescence model of antideuteron production and the influence of antideuteron measurements at particle colliders are discussed. This is followed by a review of the modeling of antideuteron propagation through the magnetic fields, plasma currents, and molecular material of our Galaxy, the solar system, the Earth's geomagnetic field, and the atmosphere. Finally, the three ongoing or planned experiments that are sensitive to cosmic-ray antideuterons, BESS, AMS-02, and GAPS, are detailed. As cosmic-ray antideuteron detection is a rare event search, multiple experiments with orthogonal techniques and backgrounds are essential. Therefore, the combination of AMS-02 and GAPS antideuteron searches is highly desirable. Many theoretical and experimental groups have contributed to these studies over the last decade, this review aims to provide the first coherent discussion of the relevant dark matter theories that antideuterons probe, the challenges to predictions and interpretations of antideuteron signals, and the experimental efforts toward cosmic antideuteron detection. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physrep.2016.01.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Previous experimental studies of superradiance (SR) in multi-level systems have been explainable using the predictions of the well-known simple two-level SR model. However our recent study [K. Nakajima et al., J. Phys. Soc. Jpn. 84, 054301 (2015)] using EUV free-electron laser excitation of helium atoms, where SR was observed at wavelengths of 502, 668, and 728 nm, revealed behaviour which necessitates a full multi-level treatment of the SR development. In this paper, we report simulations of the initial excitation by the FEL pulses, and the subsequent development of multi-level SR. The results of the simulation reproduce the experimental findings, and reveal that competitive SR on two transitions with a common upper level plays an important role in the development of the system.

DOI： 10.7566/JPSJ.85.034301

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

We investigate a potential candidate for a future optical clock: the nucleus of the isotope Th-229. Over the past 40 years of research, various experiments have found evidence for the existence of an isomeric state at an energy of a few eV. So far, neither the energy nor the lifetime of the isomer have been determined directly. As the scene is not yet prepared for direct laser excitation, other means of populating the isomer need to be explored. We investigate three different approaches, all of which rely on CaF2 crystals doped with Th-229 or U-233. Various kinds of crystal luminescence are discussed in detail.

DOI： 10.1088/1742-6596/723/1/012059

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

SPAN (SPectroscopy of Atomic Neutrino) project aims to determine the absolute neutrino mass. The process we plan to use is a cooperative de-excitation of atoms in a metastable level emitting a neutrino pair associated with a photon. The photon energy spectrum of this process contains information on the absolute mass of neutrino. Key items of this experiment are a rate amplification using macro-coherence in a target medium in case of plural particles emission and an external triggering of the emission in order to scan the spectrum. We have demonstrated the rate amplification in two-photon emission from para-hydrogen gas which was coherently excited to its first vibrationally excited state. The coherence in the medium was generated by irradiating two driving laser pulses. The emission was stimulated by irradiating a mid-infrared laser pulse. The enhancement factor of more than 10(18) with respect to the spontaneous emission was achieved. This paper briefly summarizes the results.

DOI： 10.1088/1742-6596/718/6/062043

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_577

CiNii Article

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_181

CiNii Article

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 10(15) from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect.

DOI： 10.1007/s10751-015-1177-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A readout module for PPD/MPPC/GAPD/SiPM is developed using EASIROC ASIC. The module can handle 64 PPDs and has on-board bias power supply, ADC for energy measurement, 1 ns TDC on FPGA as well as 64ch Logic output for external trigger. Controls and data transfer are through SiTCP technology implemented in FPGA. The module has NIM format for convenience, but can be operated without crate with 5 V AC/DC converter. Basic performance of production module was tested and the results are presented in the poster. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2015.01.098

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS INC  

We report coherent enhancement of two-photon emission from the excited
vibrational state of molecular hydrogen triggered by irradiating mid-infrared
pulses externally. We previously observed the two-photon emission triggered by
the internally generated fourth Stokes photons. By injecting independent
mid-infrared pulses externally, it is possible to control experimental
parameters and investigate the mechanism in more detail. In this article, we
describe the two-photon emission using the external trigger pulses. Its
spectrum and dependence on the energy and timing of the trigger pulse are
presented along with numerical simulations based on the Maxwell-Bloch
equations. The measured number of emitted photons is 6 10^11 photons/pulse and
the resulting enhancement factor from the spontaneous emission is more than
10^18. This value is three orders of magnitude higher than that of the previous
experiment. External control of emission process is expected to be essential
for observation of weaker process of radiative emission of neutrino pair.

DOI： 10.1093/ptep/ptv103

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arXiv

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Other Link： http://arxiv.org/pdf/1505.07663v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS INC  

A scheme of quantum electrodynamic (QED) background-free radiative emission of a neutrino pair (RENP) is proposed in order to achieve precision determination of neutrino properties so far not accessible. The important point for the background rejection is the fact that the dispersion relation between the wave vector along the propagating direction in the wave guide (and in a photonic-crystal-type fiber) and the frequency is modified by a discretized non-vanishing effective mass. This effective mass acts as a cutoff of allowed frequencies, and one may select the RENP photon energy region free of all macro-coherently amplified QED processes by choosing the cutoff larger than the mass of neutrinos.

DOI： 10.1093/ptep/ptv064

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arXiv

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Other Link： http://orcid.org/0000-0001-8190-2863

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The cosmic background neutrino of temperature 1.9 K affects rates of radiative emission of neutrino pairs (RENP) from metastable excited atoms, since its presence blocks the pair emission by the Pauli exclusion principle. We quantitatively investigate how the Pauli blocking distorts the photon energy spectrum and calculate its sensitivity to cosmic parameters such as the neutrino temperature and its chemical potential. Important quantities for high sensitivities to these parameter measurements are found to be the level spacing of atomic deexcitation and the unknown mass value of the lightest neutrino, in particular, their relationship to one another.

DOI： 10.1103/PhysRevD.91.063516

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arXiv

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Other Link： http://orcid.org/0000-0001-8190-2863

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_668

CiNii Article

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_86

CiNii Article

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Laser-induced near-infrared (NIR) emission spectra of neutral bismuth timer, Bi-3, embedded in solid neon matrixes at 3 K were recorded in a range 870-1670 nm. Using photoexcitation with low energy photons at 1064 nm, two emission band systems were newly identified by their origin bands at T-0 = 6600 and 8470 cm(-1). Accordingly, spectral assignment for three NIR emission band systems reported recently was partly revised for the one with its origin band at T-0 = 7755 cm(-1) and reconfirmed for the others at T-0 = 9625 and 11 395 cm(-1). Energy splitting by spin-orbit coupling between the pair of electronic energy levels in the ground state of bismuth trimer, Bi-3, both having a totally symmetric vibrational mode of frequency at omega"(e) = 150 cm(-1), was determined to be 1870 +/- 1.5 cm(-1). Transitions from the pair of electronically excited states, locating at T-0 = 8470 and 9625 cm(-1) above the ground state and separated by spin-orbit coupling of 1155 cm(-1), have relatively long decay constants of tau similar to 0.2 and similar to 0.1 ms, respectively.

DOI： 10.1021/jp509714f

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of Science (PoS)  

The Balloon-Borne Experiment with a Superconducting Spectrometer (BESS-Polar II) flew suc- cessfully over Antarctica for 24.5 days in December 2007 through January 2008 during a period of minimum solar activity. BESS-Polar II is concentrically arranged with various particle detectors and a solenoidal superconducting magnet that allow it to accurately identify hydrogen and helium isotopes among the incoming Galactic cosmic-ray nuclei. 2H and 3He are mostly secondary par- ticles produced after interaction of primary 1H and 4He cosmic rays during their propagation in the interstellar medium. The high mass separation of BESS-Polar II, the long-duration balloon flight and the stability of the instrument provide unprecedented high precision measurements of light isotopes. This paper will present new measurements of hydrogen and helium isotopes with energies from 0.2 GeV/nucleon up to about 1.5 GeV/nucleon, which gives essential information to better understand the history of cosmic-ray propagation in the Galaxy. They will be compared to previous results and theoretical calculations using GALPROP.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of Science (PoS)  

The energy spectra of cosmic-ray protons and helium near solar minimum were measured with BESS-Polar (Balloon-borne Experiment with a Superconducting Spectrometer-Polar) during long-duration flights over Antarctica in December 2004 and December 2007, and are discussed here. The absolute fluxes and spectral shapes of primary protons and helium probe the origin and the propagation history of cosmic rays in the Galaxy. The spectra are also essential as inputs to calculate the spectrum of cosmic-ray antiprotons, which are secondary products of cosmic-ray interactions with the interstellar gas. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160 GeV and helium nuclei 0.2-80 GeV/nucleon [1].

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DOI： 10.1103/PhysRevD.90.013022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS INC  

In this paper, we describe an experiment which was conducted to explore the
macro-coherent amplification mechanism using a two-photon emission process from
the first vibrationally-excited state of para-hydrogen molecule. Large
coherence in the initial state was prepared by the adiabatic Raman population
transfer method, and the lowest Stokes sideband was used as a trigger field. We
observed the coherent two-photon emission consistent with the expectation of
the paired super-radiance master equation.

DOI： 10.1093/ptep/ptu152

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arXiv

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Other Link： http://arxiv.org/pdf/1406.2198v2

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) is configured with a solenoidal superconducting magnet and a suite of precision particle detectors, including time-of-flight hodoscopes based on plastic scintillators, a silica-aerogel Cherenkov detector, and a high resolution tracking system with a central jet-type drift chamber. The charges of incident particles are determined from energy losses in the scintillators. Their magnetic rigidities (momentum/charge) are measured by reconstructing each particle trajectory in the magnetic field, and their velocities are obtained by using the time-of-flight system. Together, these measurements can accurately identify helium isotopes among the incoming cosmic-ray helium nuclei up to energies in the GeV per nucleon region. The BESS-Polar I instrument flew for 8.5 days over Antarctica from December 13th to December 21st, 2004. Its long-duration flight and large geometric acceptance allow the time variations of isotopic fluxes to be studied for the first time. The time variations of helium isotope fluxes are presented here for rigidities from 1.2 to 2.5 GV and results are compared to previously reported proton data and neutron monitor data. Published by Elsevier Ltd. on behalf of COSPAR.

DOI： 10.1016/j.asr.2013.09.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

We describe in this paper a fast and efficient method of producing a high density of barium (Ba) atoms in the D-1(2) metastable state, which is a candidate initial state for a new class of cooperative and coherent optical process called paired superradiance (PSR). In the experiment, Ba atoms are excited first by laser light to the P-1(1) state and then brought to the desired state D-1(2) via radiative transition in the superradiance (SR) mode. It is found that a production efficiency (from S-1(0) to D-1(2)) of more than similar to 30% is achieved within a time interval of a few nanoseconds for a Ba density n > 10(19) m(-3). Several key features of SR important for future PSR experiments are also studied.

DOI： 10.7566/JPSJ.83.044301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS INC  

It has recently been argued that atoms and molecules may become good targets for determining neutrino parameters still undetermined, if the atomic/molecular process is enhanced by a new kind of coherence. We compute the photon energy spectrum rate arising from coherent radiative neutrino pair emission processes of metastable excited states of I-2 and its isovalent molecules, vertical bar Av &gt; -&gt; vertical bar Xv'&gt; + gamma +nu(i)nu(j) and vertical bar A' v &gt; -&gt; vertical bar Xv '&gt; + gamma + nu(i)nu(j), with gamma an IR photon and nu(i(j)) the i (j)th neutrino mass eigenstates, and show how fundamental neutrino parameters may be determined. Energies of electronically excited states of I-2, including the effect of spin-orbit couplings, were calculated by the multiconfigurational second-order perturbation (CASPT2) method. Summation over many vibrational levels of intermediate states is fully incorporated. Unlike atomic candidates with a much larger energy difference, such as Xe, I-2 transitions from a vibrational level A(v = 0) to X(v' = 24) give us an opportunity to determine the mass type (Majorana vs Dirac distinction) and theMajorana CPV (charge-conjugation parity violating) phases, although the rate is much smaller.

DOI： 10.1093/ptep/ptt118

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Publishing type：Research paper (international conference proceedings)   Publisher：Sissa Medialab  

DOI： 10.22323/1.158.0007

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Language：English   Publishing type：Research paper (scientific journal)  

The process of collective de-excitation of atoms in a metastable level into emission mode of a single photon plus a neutrino pair, called radiative emission of neutrino pair (RENP), is sensitive to the absolute neutrino mass scale, to the neutrino mass hierarchy and to the nature (Dirac or Majorana) of massive neutrinos. We investigate how the indicated neutrino mass and mixing observables can be determined from the measurement of the corresponding continuous photon spectrum taking the example of a transition between specific levels of the Yb atom. The possibility of determining the nature of massive neutrinos and, if neutrinos are Majorana fermions, of obtaining information about the Majorana phases in the neutrino mixing matrix, is analyzed in the cases of normal hierarchical, inverted hierarchical and quasi-degenerate types of neutrino mass spectrum. We find, in particular, that the sensitivity to the nature of massive neutrinos depends critically on the atomic level energy difference relevant in the RENP. © 2013 Elsevier B.V.

DOI： 10.1016/j.physletb.2013.01.015

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arXiv

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Other Link： http://orcid.org/0000-0001-8190-2863

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) was flown from Lynn Lake, Manitoba, Canada in August, 2000, during the maximum solar modulation period, with an average residual atmospheric overburden of 4.3 g/cm(2). Precise spectral measurements of cosmic ray hydrogen isotopes from 0.178 GeV/n to 1.334 GeV/n were made during the 28.7 h of flight. This paper presents the measured energy spectra and their ratio, H-2/H-1. The results are also compared with previous measurements and theoretical predictions. (c) 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2012.01.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The balloon-borne experiment with a superconducting spectrometer (BESS) has performed cosmic-ray observations as a US-Japan cooperative space science program, and has provided fundamental data on cosmic rays to study elementary particle phenomena in the early Universe. The BESS experiment has measured the energy spectra of cosmic-ray antiprotons to investigate signatures of possible exotic origins such as dark matter candidates or primordial black holes, and searched for heavier antinuclei that might reach Earth from antimatter domains formed in the early Universe. The apex of the BESS program was reached with the Antarctic flight of BESS-Polar II, during the 2007-2008 Austral Summer, that obtained over 4.7 billion cosmic-ray events from 24.5 days of observation. The flight took place at the expected solar minimum, when the sensitivity of the low-energy antiproton measurements to a primary source is greatest. Here, we report the scientific results, focusing on the long-duration flights of BESS-Polar I (2004) and BESS-Polar II (2007-2008). (c) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2011.07.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The coherence decay of the v = 2 vibrational state (vibrons) of solid parahydrogen was measured via time-resolved coherent anti-Stokes Raman spectroscopy. We found that the decay curve has a non-exponential time profile in the time scale of 200 ns at a low temperature below 5 K and a low orthohydrogen impurity concentration (similar to 0.01%). This behavior, as also observed in the case of the v = 1 vibrons, represents a signature of band structure of the v = 2 state in the solid phase. The maximum coherence decay time of 50 ns in an exponential part was achieved, which shows excellence of the v = 2 state for coherent processes. We also found that finite temperatures, orthohydrogen impurities, and other structural inhomogeneity accelerate the decay, hiding the non-exponential feature of the vibron band. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773893]

DOI： 10.1063/1.4773893

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Laser induced fluorescence (LIF) spectroscopy was applied to small bismuth clusters embedded in a solid neon matrix at 3 K. Near infrared (NIR) optical emission spectra were recorded in a range of 6200-11 600 cm(-1) by an excitation with 1.79 eV photons using a pulsed dye laser system. Three new NIR band systems were identified by their origin bands at 8207, 9625 and 11 395 cm(-1). Each of the NIR systems exhibited the vibrational progression with a common lower state frequency at 151 cm(-1). Temporal decay profiles for selected NIR emission bands showed upper state lifetimes on the order of a hundred of microseconds, explainable by the transition between mixed spin states. Low-lying electronic states for small bismuth clusters, Bi-n (n = 2-4), are discussed along the theory and experiment reported so far.

DOI： 10.1140/epjd/e2012-30529-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We studied diffusion of hydrogen fluoride (HF) in solid parahydrogen (pH(2)) around 4 K. Diffusion rates were determined from time dependence of FT-IR spectra of HF monomers. The absorption of HF monomers shows temporal decay due to dimerization reaction via diffusion. It was found that the rates are affected by the sample temperature, the initial HF concentration, and annealing of samples. The observed non-Arrhenius-type temperature dependence suggests that the diffusion is dominated by a quantum tunneling process, that is, "quantum diffusion." Deceleration of the diffusion in condensed samples and acceleration in annealed samples were also observed. These results can be attributed to the fact that lower periodicity of samples due to impurities or defects suppresses the quantum tunneling. It seems to be difficult to explain the observed dependences by three possible diffusion mechanisms, exchange of chemical bonds, direct cyclic exchange, and exchange with mobile vacancy. Therefore, we propose a hypothetical mechanism by exchange of vacancies originating from quantum effect. (C) 2013 AIP Publishing LLC.

DOI： 10.1063/1.4808035

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Sociedade Brasileira de Fisica  

BESS (Balloon-borne Experiment with a Superconducting Spectrometer) had its first circumpolar flight from Williams Field near McMurdo Station, Antarctica from Dec. 13 to 21, 2004. We have analyzed proton fluxes for this flight to study short-term variations in their intensities. Throughout a balloon flight, altitude varies, and, as a result, the atmospheric overburden changes. Precise determination of primary particle fluxes at the top of Earth’s atmosphere, requires a detailed correction for the effects of atmosphere on the fluxes observed by the detector. We carried out a careful analysis of BESS-Polar I data by dividing the whole flight data set into intervals of 4 hours. Then primary proton fluxes were individually determined for each of these time intervals after applying individual atmospheric corrections for each of these 4-hour intervals. Our sub-1% precision measurements of BESS Polar-I proton relative fluxes exhibit short-term variations after all instrumental effects are removed. The time progression of proton flux has two main features
a rising flux at the beginning of the flight, followed by quasi-periodic variation. Although the Sun was primarily quiet, arrival of a high-speed solar wind stream, enhancement of the interplanetary magnetic field, and a high energy multiple eruption solar energetic particle event occurred around this flight. In addition, the BESS-Polar I flight commenced during the recovery phase of a Forbush decrease. We present BESS-Polar I proton flux progression as a function of energy between 0.1 - 100.0 GeV and suggest possible physical interpretations of the observed variations in relation with interplanetary structures in the near-Earth space.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

For the J-PARC E40 experiment which aims to measure differential cross-sections of Sigma p scatterings, a system to detect scattered proton from Sigma p scatterings is under development. The detection system consists of scintillation fibers with a MPPC readout. A prototype and a readout electronics for MPPC have already been developed. The prototype consisting of a scintillation fiber tracker and a BGO calorimeter was tested with a proton beam of 80 MeV. Energy resolutions of the tracker of 22.0% (sigma) and the calorimeter of 1.0% (sigma) were obtained for 1 MeV and 70 MeV energy deposit, respectively. The prototype readout electronics has an ASIC for multichannel operation. EASIROC, and a Silicon TCP (SiTCP) interface to communicate with a DAQ system. Its data transfer rate measured was 14 kHz. Required performances for the prototype system have been achieved except for the energy resolution of the prototype fiber tracker. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2011.10.005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to similar to 2 mu m diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2011.11.053

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We develop for dipole-forbidden transition a dynamical theory of two-photon paired superradiance (PSR). This is a cooperative process characterized by two photons emitted back to back with equal energies. By irradiating the trigger laser from two target ends, with its frequency tuned at the half energy between two levels, a macroscopically coherent state of medium and fields dynamically emerges as time evolves, and a large signal of amplified output occurs with a time delay. The basic semiclassical equations in 1 + 1 space-time dimensions are derived for the field-plus-medium system to describe the space-time evolution of the entire system and are numerically solved to demonstrate the existence of both explosive and weak PSR phenomena in the presence of relaxation terms. The explosive PSR event terminates accompanying a sudden release of most of the energy stored in the target. Our numerical simulations are performed using the vibrational transition X-1 Sigma(+)(g)upsilon = 1 -&gt; 0 of a para-H-2 molecule and taking many different excited atom number densities and different initial coherences between the metastable and the ground states. In an example with a number density close to O(10(21) cm(-3)) and a high initial coherence, the explosive event terminates several nanoseconds after the trigger irradiation, when the phase relaxation time larger than O(10 ns) is taken. After PSR events the system is expected to follow a steady-state solution which is obtained by analytic means and is made of many objects of field condensates endowed with a topological stability.

DOI： 10.1103/PhysRevA.86.013812

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arXiv

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Other Link： http://orcid.org/0000-0001-8190-2863

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The international Muon Ionization Cooling Experiment (MICE), which is under construction at the Rutherford Appleton Laboratory (RAL), will demonstrate the principle of ionization cooling as a technique for the reduction of the phase-space volume occupied by a muon beam. Ionization cooling channels are required for the Neutrino Factory and the Muon Collider. MICE will evaluate in detail the performance of a single lattice cell of the Feasibility Study 2 cooling channel. The MICE Muon Beam has been constructed at the ISIS synchrotron at RAL, and in MICE Step I, it has been characterized using the MICE beam-instrumentation system. In this paper, the MICE Muon Beam and beam-line instrumentation are described. The muon rate is presented as a function of the beam loss generated by the MICE target dipping into the ISIS proton beam. For a 1 V signal from the ISIS beam-loss monitors downstream of our target we obtain a 30 KHz instantaneous muon rate, with a neglible pion contamination in the beam.

DOI： 10.1088/1748-0221/7/05/P05009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

In two long-duration balloon flights over Antarctica, the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) collaboration has searched for antihelium in the cosmic radiation with the highest sensitivity reported. BESS-Polar I flew in 2004, observing for 8.5 days. BESS-Polar II flew in 2007-2008, observing for 24.5 days. No antihelium candidate was found in BESS-Polar I data among 8.4 x 10(6) vertical bar Z vertical bar = 2 nuclei from 1.0 to 20 GV or in BESS-Polar II data among 4: 0 x 10(7) vertical bar Z vertical bar = 2 nuclei from 1.0 to 14 GV. Assuming antihelium to have the same spectral shape as helium, a 95% confidence upper limit to the possible abundance of antihelium relative to helium of 6.9 x 10(-8) was determined combining all BESS data, including the two BESS-Polar flights. With no assumed antihelium spectrum and a weighted average of the lowest antihelium efficiencies for each flight, an upper limit of 1.0 x 10(-7) from 1.6 to 14 GV was determined for the combined BESS-Polar data. Under both antihelium spectral assumptions, these are the lowest limits obtained to date.

DOI： 10.1103/PhysRevLett.108.131301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The energy spectrum of cosmic-ray antiprotons ((p) over bar 's) from 0.17 to 3.5 GeV has been measured using 7886 (p) over bar 's detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary (p) over bar calculations. Cosmologically primary (p) over bar 's have been investigated by comparing measured and calculated (p) over bar spectra. BESS-Polar II data show no evidence of primary (p) over bar 's from the evaporation of primordial black holes.

DOI： 10.1103/PhysRevLett.108.051102

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.67.1.1.0_74_3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS INC  

We systematically investigate the new experimental method of using atoms or molecules to measure the important parameters of neutrinos that are still to be determined: the absolute mass scale, the mass hierarchy pattern (normal or inverted), the neutrino mass type (Majorana or Dirac), and the CP-violating phases, including Majorana phases. Most of these observables are difficult to measure in neutrino oscillation experiments. There are advantages to using atomic targets, such as the closeness of available atomic energies to anticipated neutrino masses, over nuclear target experiments such as the end point spectrum of beta decay and two-electron line spectrum in the neutrinoless double beta decay, both of which address some of the overlapping objectives with atomic/molecular experiments. A disadvantage of using atomic targets, the smallness of rates, is overcome by the macro-coherent amplification mechanism. The atomic or molecular process we use is a cooperative deexcitation of a collective body of atoms in a metastable level vertical bar e > emitting a neutrino pair and a photon: vertical bar e > -> vertical bar g > + gamma + nu(i)nu(j), where nu(i)s are neutrino mass eigenstates. The macro-coherence is developed by trigger-laser irradiation of two colors, which frequently causes the two-photon process vertical bar e > <-> vertical bar g > + gamma + gamma, vertical bar e > + gamma <-> vertical bar g > + gamma inside the target. We discuss important aspects of the macro-coherence development in detail, by setting up the master equation for the target Bloch vector (whose components are population difference and medium polarization) and the propagating electric field. Our master equation includes the effects of phase decoherence of medium polarization and decay of population difference. The spectral rate (the number of events per unit time) of macro-coherent radiative emission of a neutrino pair has three parts, and is given by a factorized formula of the form (overall omega-independent rate denoted by Gamma(0)) x (spectral shape function denoted by I (omega)) x (time-evolving dynamical factor), where omega is the photon energy. The constant factor Gamma(0) determines the overall rate in the unit of 1/time, and for Xe it is of the order of 1Hz(n/10(22) cm(-3))(3) (V/10(2) cm(3)). The dynamical factor is time dependent and is given by the space integrated quantity, over the entire target, of the product of the magnitude squared of the coherent polarization and the field strength (in the units of the maximally extractable energy density) stored inside the target. The asymptotic value of the time-evolving dynamical factor is given by the contribution of the field condensate accompanied by macroscopic coherence, which is calculated using the static limit of the master equation. With an appropriate choice of heavy target atoms or molecules such as Xe and I-2 that have a large M1 x E1 matrix element between vertical bar e > and vertical bar g >, we show that one can determine three neutrino masses along with distinction of the mass hierarchy pattern (normal or inverted) by measuring the spectral shape I (omega).If one uses a target of available energy of a fraction of 1 eV, the most experimentally challenging observable, the Majorana CP phases may be determined, comparing the detected rate with differences of theoretical expectations which exist at the level of several percent. The Majorana CP-violating phase is expected to be crucial to the understanding of the matter-antimatter imbalance in our universe. Our master equation, when applied to E1 x E1 transitions such as pH(2) vibrational Xv = 1 -> 0, can describe explosive paired superradiance events in which most of the energy stored in vertical bar e > is released in the order of a few nanoseconds. The present paper is intended to be self-contained, explaining some details of related theoretical works in the past, and reports on new simulations and the ongoing experimental efforts of the project to realize neutrino mass spectroscopy using atoms/molecules.

DOI： 10.1093/ptep/pts066

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Charged-particle tracking in the international Muon Ionisation Cooling Experiment (MICE) will be performed using two solenoidal spectrometers, each instrumented with a tracking detector based on 350 mu m diameter scintillating fibres. The design and construction of the trackers is described along with the quality-assurance procedures, photon-detection system, readout electronics, reconstruction and simulation software and the data-acquisition system. Finally, the performance of the MICE tracker, determined using cosmic rays, is presented. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2011.04.041

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of High Energy Physics  

BESS (Balloon-borne Experiment with a Superconducting Spectrometer) had its first circumpolar flight from Williams Field near McMurdo Station, Antarctica from Dec. 13 to 21, 2004. Our sub-1% precision reveals BESS-Polar I proton fluxes exhibit transient variations at the few1% level. The time progression of proton flux has three main features
a rising flux at the beginning of the flight, a transition region around Dec. 17, followed by quasi-periodic variation. Neutron monitor data show that the BESS-Polar I flight occurred during the recovery phase of a small Forbush decrease. The solar wind plasma and particle data show that this flight took place during the tail end of a high-energy, multiple-eruption solar energetic particle (SEP) event. A high speed solar wind stream arrived near the Earth around Dec. 17, 2004. We present the flux progression as a function of energy between 0.1 - 100.0 GeV and suggest possible physical interpretations.

DOI： 10.7529/ICRC2011/V02/1247

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of High Energy Physics  

Although cosmic-ray antideuterons can be produced in primary cosmic-ray interactions with the interstellar medium in the same way as cosmic-ray antiprotons, the probability is much smaller, especially at low energies, because of the very low production cross-section and strict kinematic requirement compared to secondary antiproton production. The lack of significant astrophysical background indicates that a search for low-energy antideuterons could be a good probe for a novel production mechanisms such as pair-annihilation of neutralino dark matter or evaporation of primordial black holes. The BESS-Polar program has accumulated cosmic-ray data in near solar minimum conditions with more than ten times the statistics of those obtained by BESS flights during the previous solar minimum period. Based on these data, we perform a new antideuteron search with unprecedented sensitivity.

DOI： 10.7529/ICRC2011/V05/1259

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of High Energy Physics  

The first flight of the Balloon-Borne Experiment with a Superconducting Spectrometer (BESS-Polar I) in Antarctica collected about 900 million cosmic ray events during 8.5 days in 2004. Particle charge was determined from energy loss in the scintillators, rigidity by reconstructing each particle trajectory in the magnetic field, and velocity by utilizing time of flights counters. These measurements can clearly identify hydrogen and helium isotopes among the incoming particles. These isotopes are generally believed to result from nuclear interactions of primaries with the interstellar medium. Measurement of their flux is expected to provide important information on cosmic ray sources and particle propagation in interstellar space. The presentation will focus on determination of the helium isotope flux in the kinetic energy per nucleon range 0.1 GeV/n to about 1.5 GeV/n. After quickly introducing the BESS-Polar I detector, the dedicated analysis to differentiate isotopes will be described. Finally, the energy spectra will be presented and compared to previous measurements.

DOI： 10.7529/ICRC2011/V06/0699

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of High Energy Physics  

We have searched for antihelium in cosmic-rays since 1993 using a series of nine conventional BESS northern latitude balloon flights and two long-duration BESS-Polar Antarctic balloon flights. The BESS-Polar spectrometer is an evolutionary development of the previous BESS instruments, adapted to long duration flight. No antihelium candidate was found in the rigidity ranges of 0.6-20 GV among 8 × 106 helium nuclei events for BESS-Polar I and in the rigidity range of 0.6-14 GV among 4 × 107 events for BESS-Polar II, respectively. A resultant upper limit of 6.9 × 10 -8 for the abundance ratio of antihelium/helium at the top of the atmosphere in the rigidity range of 1-14 GV was set by combining all the BESS and BESS-Polar flight data. This is the most stringent limit obtained to date.

DOI： 10.7529/ICRC2011/V05/1230

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of High Energy Physics  

The energy spectrum of cosmic-ray antiprotons (p's) has been measured in the range 0.17 to 3.5 GeV, based on 7886 p's collected by the BESS-Polar II instrument during a long duration flight over Antarctica in a Solar minimum period of December 2007 through January 2008. The p spectrum measured by BESS-Polar II shows good consistency with the secondary p calculations. Given this background of secondary p's, cosmologically primary p's have been searched for using the observed p spectrum. BESS-Polar II result shows no evidence of primary p's that originated from the evaporation of PBH.

DOI： 10.7529/ICRC2011/V06/1280

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.66.1.1.0_28_4

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The Muon Ionization Cooling Experiment (MICE) is a strategic R&D project intended to demonstrate the only practical solution to providing high brilliance beams necessary for a neutrino factory or muon collider. MICE is under development at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. It comprises a dedicated beamline to generate a range of input muon emittances and momenta, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. The emittance of the incoming beam will be measured in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in Liquid Hydrogen (LH2) absorbers to RF cavity acceleration. A second spectrometer, identical to the first, and a second muon identification system will measure the outgoing emittance. In the 2010 run at RAL the muon beamline and most detectors were fully commissioned and a first measurement of the emittance of the muon beam with particle physics (time-of-flight) detectors was performed. The analysis of these data was recently completed and is discussed in this paper. Future steps for MICE, where beam emittance and emittance reduction (cooling) are to be measured with greater accuracy, are also presented.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report measurements of FT-IR absorption spectroscopy of HF, DF, and their clusters in solid parahydrogen (pH(2)). The observed spectra contain many absorption lines which were assigned to HF monomers, HF polymers, and clusters with other species, such as N-2, O-2, orthohydrogen (oH(2)), etc. The rotational constants of HF and DF monomers were determined from the cooperative transitions of the vibration of solid pH(2) and the rotation of HF and DF. Small reduction of the rotational constants indicates that HF and DF are nearly free rotors in solid pH(2). Time dependence of the spectra suggests that HF and DF monomers migrate in solid pH(2) and form larger polymers, probably via tunneling reactions through high energy barriers on inserting another monomer to the polymers. The line width of HF monomers in solid pH(2) was found to be 4 cm(-1), which is larger than that of other hydrogen halides in solid pH(2). This broad line width is explained by rapid rotational relaxation due to the accidental coincidence between the rotational energy of HF and the phonon energy with maximum density of states of solid pH(2) and the rotational translational coupling in a trapping site.

DOI： 10.1021/jp207419m

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SCUOLA INT SUPERIORE STUDI AVANZATI-SISSA  

The primary aims of the BESS-Polar program are precise measurements of the low-energy antiproton spectrum and search for cosmologically significant antimatter, which would provide new clues to understand the early Universe. The second flight (BESS-Polar II) over Antarctica was successfully carried out in Dec 2007 - Jan 2008. We performed 24.5days scientific observation just at the solar minimum. The payload worked well during the flight and 4.7 billion cosmic-ray events were collected. Based on the BESS-Polar II data, we present recent preliminary results of cosmic-ray antiproton measurements and sensitive search for antimatter.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

This document summarizes the work of the Accelerator Working Group (AWG) of the International Scoping Study (ISS) of a Future Neutrino Factory and Superbeam Facility. The main goal of the activity was to reach consensus on a baseline design for a Neutrino Factory complex, including proton driver parameters, choice of target, front-end design, acceleration system design, and decay ring geometry. Another goal was to explore the commonality, if any, between the proton driver for a Neutrino Factory and those for a Superbeam or Beta Beam facility. In general, the requirements for either of the latter facilities are less stringent than those for a Neutrino Factory. Here, we discuss concepts, parameters, and expected performance of the required subsystems for our chosen baseline design of a Neutrino Factory. We also give an indication of the main R&D tasks-many of which are already under way-that must be carried out to finalize facility design approaches.

DOI： 10.1088/1748-0221/4/07/P07001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

An ultra-thin superconducting solenoid has been developed for a cosmic-ray spectrometer ballooning over Antarctica, which is named BESS-Polar II. The coil with a diameter of 0.9 m, a length of 1.4 m and a thickness of 3.5 mm, is wound with high-strength aluminum stabilized superconductor and provides 0.8 T in the spectrometer. Based on the experience at the BESS-Polar-I solenoid flight for nine days in 2004, the BESS-Polar-II solenoid, which was cryogenically improved, realized a persistent current mode operation for 25 days in the second flight campaign in December 2007 though January 2008. It has contributed to accumulate the cosmic-ray observation data with 4700 million events and 16 terabyte in a hard disk unit. This report will describe the second solenoid performance during the flight.

DOI： 10.1109/TASC.2009.2017946

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Physical Society of Japan  

The aims of the BESS-Polar experiment are precise measurements of the low-energy antiproton spectrum and search for cosmologically significant antimatter. After its first flight (BESS-Polar I), we had developed a new spectrometer based on the feedback from the results. Most of the detector components had been redesigned and upgraded to improve their performance and to increase the data taking period and capacity. The second flight (BESS-Polar II) was successfully carried out in December 2007- January 2008. We performed 24.5 days scientific observation just at the solar minimum. In this paper, BESS-Polar II instrument and flight summary will be presented. © 2009 The Physical Society of Japan.

DOI： 10.1143/JPSJS.78SA.29

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：University of Lodz  

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS-Polar I) was flown successfully 13 - 21 December 2004 for the first time in Antarctica. A total number of 900 million cosmic-ray events were recorded from the 8-day, 13-hour flight. The polar region allowed for a reduction in the detectable rigidity to about 0.26 GV. The energy loss in the scintillators provided charge measurements to separate protons and helium nuclei. Particle trajectories in the magnetic field provided rigidity measurements. Time-of-Flight counters provided particle velocity measurements to identify isotopes. The data selection procedure for hydrogen and helium isotopes and the mass histograms of hydrogen isotope, 2H, measured with the BESS-Polar I flight are presented in this paper.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The BESS-Polar spectrometer had its first successful balloon flight over Antarctica in December 2004. During the 8.5-day long-duration flight, almost 0.9 billion events were recorded and 1,520 antiprotons were detected in the energy range 0.1-4.2 GeV. In this Letter, we report the antiproton spectrum obtained, discuss the origin of cosmic-ray antiprotons, and use antiproton data to probe the effect of charge-sign-dependent drift in the solar modulation. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physletb.2008.10.053

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The first scientific flight of the BESS-Polar balloon-borne experiment was successfully carried out in December 2004 from Antarctica with the primary scientific objectives of searching for primordial antiparticles from the universe and making precision measurements of primary cosmic-ray fluxes. During the 8.5 day flight, the newly developed BESS-Polar spectrometer worked well and gathered data from 9 x 10(8) cosmic-ray events, showing its capability for making long-duration science observations. We have already started hardware development for the second experiment, which is expected to be a flight of more than 20 days during the next solar minimum period with the upgraded spectrometer. In this manuscript, progress on and prospects for the BESS-Polar experiment are described. (C) 2008 Published by Elsevier Ltd on behalf of COSPAR.

DOI： 10.1016/j.asr.2007.05.048

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

In this paper, we report searches for antilielium in cosmic rays using two recently flown magnetic rigidity spectrometers. BESS-TeV had extended rigidity with all MDR of 1.4 TV and had a flight duration of one day. BESS-Polar was optimized for collecting power. It was flown for 8.5 days and had an MDR of 240 GV. Tile former flight allows us to explore a previously unexplored rigidity band and the latter flight yields a factor of three improvement in the overall BESS limit. No antilielium candidate was found in the rigidity ranges of 1-500 GV, and 0.6-20 GV, among 7 x 10(4) events taken with BESS-TeV, and 8 X 10(6) events taken with BESS-Polar, respectively. (c) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2007.09.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) has been carried out to search for primordial antiparticles in cosmic rays. In ten flights from 1993 to 2004, it measured the cosmic-ray.antiproton spectrum in the energy range 0.1-4.2 GeV at various solar activity conditions. It also searched for antideuterons and antilielium nuclei, and it made precise measurement of cosmicray particle spectra. The BESS program has been extended to long duration balloon (LDB) flights in Antarctica (BESS-Polar) with the goal of achieving unprecedented sensitivity in the search for primordial antiparticles. This report describes recent results from BESS and progress of the BESS-Polar program. (c) 2008 Published by Elsevier Ltd on behalf of COSPAR.

DOI： 10.1016/j.asr.2007.04.069

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

High-performance production targets and other critical accelerator components intercepting intense, energetic proton beams are essential as the accelerator community envisions the next generation, multi-MW accelerators. Materials that have served the nuclear sector well may not be suitable to play such a role which demands that the material comprising the beam-intercepting element must, in addition to the long exposure which leads to accumulated irradiation damage, also endure short exposure that manifests itself as thermo-mechanical shock. The ability of materials to resist irradiation-induced degradation of its properties that control shock and fatigue is of primary interest. The need for such materials that extend beyond resistance to the neutron-driven irradiation damage of reactor components has led to an extensive search and experimentation with new alloys and composites. These new high-performance materials, which appear to possess the right combination of mechanical and physical properties, are explored through a multi-phased experimental study at Brookhaven National Laboratory (BNL). This study, which brings together the interest in accelerator targets of different facilities around the world, seeks to simulate conditions of both short and long exposure to proton beams to assess the survivability potential of these new alloys and composite materials. While thermo-mechanical shock effects have been studied in the early stages of this comprehensive effort, it is irradiation damage that is currently the focus of the study and results to-date are presented in this paper along with the status and objectives of ongoing studies. Of special interest are results depicting damage reversal through post-irradiation annealing in some of the materials. High fluences of 200 and/or 117 MeV protons provided by the BNL Linac beam that serves the isotope Production Facility were used to assess irradiation damage in these new composites and alloys. (c) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2008.02.074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Historically, there are been many searches for fractionally charged particles in the cosmic radiation. However, few searches have been performed near the top of the atmosphere. We performed a search for relativistic 2/3e charged particles in cosmic rays using data collected during four BESS balloon flights from 1997 to 2000 carried out in northern Canada. The data were analyzed by examining energy deposition in the time-of-flight scintillator hodoscopes. No candidate was found. We derive an upper limit of 4.5 x 10(-7) (cm(2) s sr)(-1) for the flux of 2,e charged particles, at the 90% confidence level. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2007.02.042

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Multi pixel Photon Counter is a novel semiconductor photon sensor which consist of 100-1600 micro APD pixels. Each piel works in limited Geiger mode with an inverse bias voltage around 80 V. The MPPC has many remarkable features such as high gain, large photon detection efficiency, low cost and tolerance for magnetic field. Fundamental properties, such as the gain, dark noise rate and inter-pixel cross-talk, have been measured with three different samples which have 100, 400, and 1600 pixels. Variation of the gain over 750 samples, and uniformity of the gain and photon sensitivity within one pixel are also evaluated. As the result of the tests, it is confirmed that the MPPC has satisfactory performance for many appplications, not only for high energy physics experiments but also for medical engineering systems. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2007.08.020

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

We measured low energy cosmic-ray proton and helium spectra in the kinetic energy range 0.215-21.5 GeV/n at different solar activities during a period from 1997 to 2002. The observations were carried out with the BESS spectrometer launched on a balloon at Lynn Lake, Canada. A calculation for the correction of secondary particle backgrounds from the overlying atmosphere was improved by using the measured spectra at small atmospheric depths ranging from 5 through 37 g/cm(2). The uncertainties including statistical and systematic errors of the obtained spectra at the top of atmosphere are 5-7% for protons and 6-9% for helium nuclei in the energy range 0.5-5 GeV/n. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.astropartphys.2007.05.001

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER  

The Balloon-Born Experiment with a Superconducting Spectrometer (BESS) has measured cosmic-ray spectra blow 1 TeV and searched for antiparticle of novel cosmic origin. The BESS program is extended to long duration balloon (LDB) flights in Antarctica (BESS-Polar) aiming at unprecedented sensitivity to search for primordial antiparticles. This report describes recent results from BESS and the progress in the BESS-Polar program.

DOI： 10.1016/j.nuclphysbps.2006.12.092

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Language：English   Publisher：ELSEVIER SCIENCE BV  

DOI： 10.1016/j.physletb.2006.12.046

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Universidad Nacional Autonoma de Mexico  

The spectra of low-energy cosmic-ray protons and antiprotons have been measured by BESS in nine high-latitude balloon flights between 1993 and 2004. These measurements span a range of Solar activity from before the previous Solar minimum through Solar maximum and the onset of the present Solar minimum, as well as a Solar magnetic field reversal from positive to negative in 2000. Because protons and antiprotons differ only in charge sign, simultaneous measurements provide a sensitive probe of charge-dependent Solar modulation. The antiproton to proton ratio measured by BESS is consistent with simple spherically symmetric models of Solar modulation during the Sun's positive polarity phase, but requires charge-sign-dependent drift models during the negative phase. The BESS measurements are presented and compared to models of Solar modulation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Universidad Nacional Autonoma de Mexico  

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) was flown eight times from Lynn Lake, Manitoba, Canada between 1993 and 2002. The performance of the instrument was improved with essentially each successive flight, and precise spectral measurements of cosmic-ray hydrogen and helium isotopes were made during different phases of the solar modulation. This paper presents the measured isotopic spectra for the most recent solar maximum in 2000 and compares the results with previous measurements and with the theoretical prediction from the Reacceleration model. Both 1H and 2H spectra are consistent with the propagation calculation with the solar modulation parameter 1500 MV. The total He (3He + 4He) flux is in good agreement with the same modulation parameter. Fluxes of 3He and 4He require slightly higher modulation parameter.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Universidad Nacional Autonoma de Mexico  

The Search for antimatter in the galactic cosmic radiation is one of the main scientific objectives of the Balloon-borne Experiment with a Superconducting Spectrometer (BESS). A flatter antiproton spectrum below the secondary production peak at 2 GeV might suggest possible novel antiproton sources, such as evaporating black-holes or decaying super symmetric particles. The BESS-Polar experiment is designed as a highly transparent magnetic rigidity spectrometer that can precisely detect antiprotons down to energies of 0.1 GeV were a potential excess of primary antiprotons over the secondary production might be more apparent. The BESS-Polar instrument had its first successful balloon flight in December 2004, from McMurdo Station in Antarctica. During the 8.5-day long flight 900 million events were recorded. In this paper, we report antiproton and proton spectra as well as the search for antihelium.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Universidad Nacional Autonoma de Mexico  

BESS-Polar II (the 2nd phase of the BESS-Polar spectrometer) has been prepared for the next Antarctic campaign scheduled in December 2007. The aims of the experiment are precise measurements of the low-energy antiproton spectrum and search for cosmologically significant antimatter at this solar minimum period, with 5 times higher sensitivity than the previous measurements in BESS-Polar I. Most of the detector components have been redesigned and upgraded to improve their performance and to increase the data taking period and capacity.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This paper presents preliminary results from an ongoing post-irradiation analysis of materials that have been irradiated at the Brookhaven National Laboratory (BNL) Isotope facility. The effort is part of an experimental study that focuses on how prone to irradiation damage these materials are and thus what is their potential in playing the role of high power targets in the neutrino superbeam and the muon collider initiatives.

DOI： 10.1016/j.nuclphysbps.2006.02.077

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

We measured atmospheric antiproton spectra in the energy range 0.2 to 3.4 GeV, at sea level and at balloon altitude in the atmospheric depth range 4.5 to 26 g/cm(2). The observed energy spectra, including our previous measurements at mountain altitude, were compared with estimated spectra calculated on various assumptions regarding the energy distribution of antiprotons that interacted with air nuclei. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physletb.2005.11.042

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Publishing type：Research paper (international conference proceedings)  

The multi-pixel photon counter (MPPC) is a newly developed photodetector with an excellent photon counting capability. It also has many attractive features such as small size, high gain, low operation voltage and power consumption, and capability of operating in magnetic fields and in room temperature. The basic performance of samples has been measured. A gain of ∼10 is achieved with a noise rate less than 500 kHz with 1 p.e. threshold, and cross-talk probability of less than 40% at room temperature. The photon detection efficiency for green light is twice or more that of the photomultiplier tubes. It is found that the basic performance of the MPPC is satisfactory for use in real experiments. © 2006 IEEE. 6

DOI： 10.1109/NSSMIC.2006.356040

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Publishing type：Research paper (international conference proceedings)  

PRISM is in the works to build a future intense lowenergy muon source, which combines monochromaticity and high purity. In the PRISM project, an FFAG is used as the phase rotator to achieve the monochromatic muon beams. This paper will describe the design status the project.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This paper presents results of recent experimental studies focusing on the behavior of special materials and composites under irradiation conditions and their potential use as accelerator targets. The paper also discusses the approach and goals of on-going investigations on an expanded material matrix geared toward the neutrino superbeam and muon collider initiatives.

DOI： 10.1016/j.nuclphysbps.2005.05.033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Conducting pulsed target scheme has been studied as an alternative targetry solution used for a dedicated high-intense and bright muon source (PRISM). We made a conceptual design and have developed a pulse power supply and a mercury loop to be used for the proof-of-principle test.

DOI： 10.1016/j.nuclphysbps.2005.05.035

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

High power targetry is one of the major technical challenges to realize neutrino factories based on muon storage rings. Various R&D works have been carried out in the framework of international collaboration. Recent progress in a free mercury jet, material studies, and capture/focusing devices are discussed. Future prospects for R&D are briefly described. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2005.02.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

We performed a search for cosmic-ray antideuterons using data collected during four BESS balloon flights from 1997 to 2000. No candidate was found. We derived, for the first time, an upper limit of 1.9x10(-4) (m(2)s sr GeV/nucleon)(-1) for the differential flux of cosmic-ray antideuterons, at the 95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the atmosphere.

DOI： 10.1103/PhysRevLett.95.081101

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We measured radiation heating induced by secondary particles from 12-GeV primary proton beam interactions. A newly developed "cryogenic calorimeter" technique was employed to precisely Measure heat fluxes of 0.2.1 W deposited in a large copper absorber. The results were compared with calculations by using Monte-Carlo codes, MARS and PHITS. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2005.03.001

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TATA INST FUNDAMENTAL RESEARCH  

The BESS-Polar balloon payload had its first flight on December 13th-21st, 2004 (UTC) from McMurdo Station, Antarctica. The flight duration was over eight days and more than 9 x 108 cosmic-ray events were recorded. An overview of the BESS-Polar flight, the status of the antiproton analysis, and a discussion of the low-power readout electronics and data acquisition system can be found elsewhere in these proceedings. In this paper we discuss the design, testing, and flight performance of the BESS-Polar Cherenkov counter, which operated in ambient conditions outside a pressure vessel. The silica-aerogel Cherenkov radiator had a nominal index-of-refraction, n = 1.02, yielding an lower limit for the most likely photoelectron (PE) number of 7 in the center of the counter and 9 near the photomultiplier tubes.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TATA INST FUNDAMENTAL RESEARCH  

The first scientific flight of the BESS-Polar experiment was carried out in December 2004, aiming at elementary particle phenomena in the early Universe through observation of low energy antiprotons and search for antimatter in the cosmic radiation. The BESS-Polar payload was launched on December 13 from Williams Field near the US McMurdo Station in Antarctica, and circulated around the South Pole for 8 days and 17 hours. During the flight, the superconducting spectrometer including the solar-cell power supply system worked well, and two terabytes scientific data were recorded on the onboard hard disk drives. The flight was terminated on December 21, and the payload landed on the Ross Ice Shelf. The recovery operation continued for a week, and the spectrometer was recovered safely.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The Balloon-borne Experiment with a Super-solenoidal Spectrometer (BESS) instrument has been flown annually from Lynn Lake Manitoba since 1993. The instrument has been upgraded several times to improve its performance. The instalment flown in 1998 was able to detect H-2 clearly between 0.13 and 1.78 GeV/n as a result of improvements made on the time-of-flight (TOF) system. The BESS 98 data were analyzed to obtain the ratio and absolute fluxes of H-1 and H-2 over this energy range. The results were compared with different cosmic ray propagation models and their implications regarding their propagation history are discussed in this paper. (c) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2003.10.050

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TATA INST FUNDAMENTAL RESEARCH  

We report a cosmic-ray antiproton spectrum measured with the BESS balloon experiment performed in 2002, which was in an intermediate period between the solar maximum in 2000 and the coming solar minimum. The observed antiproton spectrum and the antiproton to proton ratio are crucial for further development of the drift model of the solar modulation effect which has been generally supported by the previous measurements.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We describe an experiment designed as a proof-of-principle test for a target system capable of converting a 4-MW proton beam into a high-intensity muon beam suitable for incorporation into either a neutrino factory complex or a muon collider. The target system is based on exposing a free mercury jet to an intense proton beam in the presence of a high-strength solenoidal magnetic field.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The desire of the high-energy-physics community for more intense secondary particle beams motivates the development of multi-megawatt, pulsed proton sources. T e targets needed to produce these secondary particle beams must be sufficiently robust to withstand the intense pressure waves arising from the high peak-energy deposition which an intense pulsed beam will deliver. In addition, the materials used for the targets must continue to perform in a severe radiation environment. The effect of the beam-induced pressure waves can be mitigated by use of target materials with high-yield strength and/or low coefficient of thermal expansion (CTE) [1, 2, 3]. We report here first results of an expanded study of the effects of irradiation on several additional candidate materials with high strength (AlBeMet, beryllium, Ti-V6-A14) or low CTE (a carbon-carbon composite, a new Toyota "gum" metal alloy [4], Super-Invar).

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The Balloon Borne Experiment with a Superconducting Spectrometer (BESS) has measured the energy spectrum of cosmic-ray antiprotons between 0.18 and 4.20 GeV in eight flights between 1993 and 2002. Above about I GeV, models in which antiprotons are secondary products of the interactions of primary cosmic rays with the interstellar gas agree with the BESS antiproton spectrum. Below I GeV, the data show a possible excess antiproton flux compared to secondary model predictions, suggesting the presence of an additional source of antiprotons. The antiproton/proton ratios measured between 1993 and 1999, during the Sun's positive-polarity phase, are consistent with simple models of solar modulation. However, results from the 2000 flight, following the solar magnetic field reversal, show a sudden increase in the antiproton/proton ratio and tend to favor a charge-sign-dependent drift model. To extend BESS measurements to lower energies, an evolutionary instrument, BESS-Polar, is under construction for polar flight in 2004. Published by Elsevier Ltd on behalf of COSPAR.

DOI： 10.1016/j.asr.2003.08.044

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TATA INST FUNDAMENTAL RESEARCH  

A flatter spectrum of low-energy cosmic ray antiprotons below 1 GeV measured by the BESS experiment in the last solar minimum period suggests the existence of possible novel and exotic sources of cosmic-ray antiprotons, such as evaporation of primordial black holes and annihilation of supersymmetric dark matter. In order to investigate these antiproton sources and to search for antimatter in the cosmic radiation, the BESS-Polar experiment was carried out with a NASA long duration balloon flight over Antarctica in December 2004. During this 8.5-day flight, the BESS-Polar superconducting spectrometer gathered 900 million cosmic-ray events. The data show that the newly developed particle detector system functioned well enough to observe the low energy antiprotons during the entire flight. Thus' we can expect to derive a precise energy spectrum of the low-energy antiprotons with several-times higher statistics than that from the flight of the previous solar minimum period.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TATA INST FUNDAMENTAL RESEARCH  

The isotopic composition measurements of cosmic-ray hydrogen and helium were made during the most recent period of solar maximum using the Balloon-borne Experiment with a Superconducting Spectrometer (BESS). The data selection procedure and the mass histograms for proton, helium and their isotopes of BESS-2000 are presented in this paper.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

In nine flights between 1993 and 2002, the Balloon Borne Experiment with a Superconducting Spectrometer (BESS) has measured the energy spectrum of cosmic-ray antiprotons between 0.18 and 4.20 GeV, and the spectra of protons and helium to several hundred GeV. BESS has also placed stringent upper limits on the existence of antihelium and antiduterons. Above about 1 GeV, models in which antiprotons are secondary products of the interactions of primary cosmic rays with the ISM agree with the BESS spectrum. Below I GeV, BESS data suggest the presence of an additional source of antiprotons. The antiproton/proton ratios measured between 1993 and 1999, during the Sun's positive-polarity phase, are consistent with simple models of solar modulation. Results from the 2000 flight, following the solar magnetic field reversal, show a sudden increase in the antiproton/proton ratio and tend to favor a charge-sign-dependent drift model. To extend BESS measurements to lower energies, a new instrument, BESS-Polar, is under construction for a flight from Antarctica in 2004.

DOI： 10.1016/j.nuclphysbps.2004.08.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Primary and atmospheric cosmic-ray spectra were precisely measured with the BESS-TeV spectrometer. The spectrometer was upgraded from BESS-98 to achieve seven times higher resolution in momentum measurement. We report absolute fluxes of primary protons and helium nuclei in the energy ranges, 1-540 GeV and 1-250 GeV/n, respectively, and absolute flux of atmospheric muons in the momentum range 0.6-400 GeV/c. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physletb.2004.05.019

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Language：English   Publisher：ELSEVIER SCIENCE BV  

DOI： 10.1016/j.physletb.2003.11.060

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Balloon-borne Experiment with a Superconducting Spectrometer (BESS) is a balloon-borne spectrometer to study elementary particle phenomena in the early Universe as well as the origin and the propagation of cosmic radiation. The instrument has a unique feature of a thin superconducting solenoid which enables a large acceptance with a cylindrical configuration. Nine balloon flights have been successfully carried out since 1993. In 2002, the detector was upgraded as the BESS-TeV spectrometer to extend primary cosmic-ray spectra up to 1 TeV. For further studies of low-energy antiprotons, a new spectrometer, BESS-Polar, with a ultra-thin superconducting solenoid is being developed for long duration balloon flights in Antarctica. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2003.10.051

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In order to investigate elementary particle phenomena in the early Universe, the BESS-polar experiment is proposed. It will study low-energy antiprotons and search for antinuclei in the galactic cosmic rays at the constant altitude maintained by a scientific balloon. A new superconducting spectrometer is being developed for long-duration balloon flights. In order to extend the detectable energy range of antiprotons down to 100 MeV, the thickness of materials along the trajectory of the incident particle is minimized. The spectrometer will be completed in 2003, and the first long-duration flight is planned in 2004. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.asr.2003.05.017

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

A conceptual design of the targetry for the high intensity slow muon source is presented. Based on simulation studies, critical issues are discussed and a baseline design is determined. We have started R&D works on superconducting solenoids as well as conducting targets, which is an alternative option.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Energy spectra of atmospheric secondary cosmic-ray protons and antiprotons were measured at mountain altitude, 2770 m above sea level. We observed more than 10(5) protons and 10(2) antiprotons. Our proton spectrum is generally consistent with other previous measurements. The observed antiproton spectrum suggests that the energy loss due to non-annihilation processes is less significant than that assumed in previous model calculations. (C) 2003 Published by Elsevier B.V.

DOI： 10.1016/j.physletb.2003.10.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The MuCool hydrogen-absorber R&D program is summarized. Prototype absorbers featuring thin aluminum windows and 'flow-through' or 'convection' cooling are under development for eventual power-handling tests in a proton beam and a cooling demonstration in a muon beam. Testing these prototypes and their components involves application of novel techniques.

DOI： 10.1088/0954-3899/29/8/331

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

This summary covers the physics topics that could benefit from the unprecedented flux of muons produced at the front end of the future neutrino factory. A selection of such opportunities was presented at NuFact02 and their demands on beam properties were evaluated. This summary will survey the rare muon decay experiments and the high precision measurements that could benefit from higher fluxes as well as some of the new programmes that could use very large mu(-) fluxes. A number of technological developments relevant to the neutrino factories were also discussed.

DOI： 10.1088/0954-3899/29/8/391

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The cosmic-ray proton, helium, and muon spectra at small atmospheric depths of 4.5-28 g/cm(2) were precisely measured during the slow descending period of the BESS-2001 balloon flight. The variation of atmospheric secondary particle fluxes as a function of atmospheric depth provides fundamental information to study hadronic interactions of the primary cosmic rays with the atmosphere. (C) 2003 Published by Elsevier Science B.V.

DOI： 10.1016/S0370-2693(03)00676-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A feasibility study on liquid hydrogen (LH2) absorbers for muon ionization cooling is reported. In muon ionization cooling, an LH2 absorber is required to have a high cooling power greater than 100 W to cool heat deposited by muons passing through. That heat in LH2 can be removed at either external or internal heat exchangers, which are cooled by cold helium gas. As one of the internal heat exchanger types, a convection-type absorber is proposed. In the convectiontype absorber, heat is taken away by the convection of LH2 in the absorber. The heat exchanger efficiency for the convection-type absorber is calculated. A possible design is presented. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(03)00724-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The PRISM project has been proposed to obtain a high-intensity slow muon beam. By employing two novel techniques, i.e., high-field pion capture and a longitudinal phase rotation, an intense (10(11)-10(12) mu/s), monochromatic (DeltaE/E similar or equal toa few %), and low-energy (20 MeV) muon beam can be produced. Muon beam with such features enable searches for lepton flavor violation at an unprecedented level as well as new field of muon application. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(03)00688-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

A stored-muon-beam neutrino factory may require transverse ionization cooling of the muon beam. We describe recent progress in research and development on energy absorbers for muon-beam cooling carried out by a collaboration of university and laboratory groups. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(03)00723-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The vertical absolute fluxes of atmospheric muons and muon charge ratio have been measured precisely at different geomagnetic locations by using the BESS spectrometer. The observations had been performed at sea level (30 m above sea level) in Tsukuba, Japan, and at 360 m above sea level in Lynn Lake, Canada. The vertical cutoff rigidities in Tsukuba (36.2degreesN, 140.1degreesE) and in Lynn Lake (56.5degreesN, 101.0degreesW) are 11.4 and 0.4 GV, respectively. We have obtained vertical fluxes of positive and negative muons in a momentum range from 0.6 to 20 GeV/c with systematic errors <3% in both measurements. By comparing the data collected at two different geomagnetic latitudes, we have seen an effect of cutoff rigidity. The dependence on the atmospheric pressure and temperature, and the solar modulation effect have been also clearly observed. We also clearly observed the decrease of charge ratio of muons at low momentum side with at higher cutoff rigidity region. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0927-6505(02)00195-0

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

A description is given of a new experiment to measure the muon electric dipole moment (EDM) to between sigma = 10(-24) e-cm and 10(-25) e-cm, which would be 5 to 6 orders of magnitude improvement over the current world average. Muons are stored in a magnetic ring. Precession due to Thomas precession and the magnetic moment are canceled with the proper combination of applied E and B fields. Only precession due to a non-vanishing EDM remains, resulting in a large amplification of the EDM signal. The method has general applicability to charged particles.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

In this paper a new method is presented for particles in storage rings which could reach a statistical sensitivity of 10(-27) e(.)cm for the deuteron EDM. This implies an improvement of two orders of magnitude over the present best limits on the T-odd nuclear forces xi parameter.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The BESS-Polar experiment with long-duration balloon flights at Antarctica aims at extremely sensitive measurement of low energy antiprotons to search for novel primary origins in the early Universe, and to study cosmic-ray propagation and solar modulation. The search for cosmic antimatter is a fundamental objective to study baryon asymmetry in the Universe. The BESS experiment with high rigidity resolution and large geometrical acceptance will maximize advantages of long duration flights at Antarctica where the rigidity cut-off is lowest. A very compact and thin superconducting magnet spectrometer is being developed to maximize the detector performance in low energies. The BESS-Polar project and progress of the development are described.

DOI： 10.1016/S0920-5632(02)01843-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have searched for antihelium nuclei in cosmic rays using the data obtained from balloon flights of the BESS magnetic spectrometer. The search was mainly based on track-quality selection, followed by rigidity analysis, and on the time-of-flight and dE/dx measurements by the scintillation counter hodoscope. We analysed all the data collected during 1993-2000 with a common analysis procedure. No antihelium nuclei events were found in the energy range from I to 14 GV. In order to determine a new upper limit, we have simulated the loss in the air and in the instrument of He (He) using the GEANT/GHEISHA code. Combined with the data collected in 1993 through 2000, a new 95 % confidence upper limit for the ratio of He/He at the top of the atmosphere of 6.8 x 10(-7) has been obtained to be after correcting for the interactions in the air and in the instruments.

DOI： 10.1016/S0920-5632(02)01842-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An accelerator experiment was performed using a low-energy antiproton beam to measure antiproton detection efficiency of BESS, a balloon-borne spectrometer with a superconducting solenoid. Measured efficiencies showed good agreement with calculated ones derived from the BESS Monte Carlo simulation based on GEANT/GHEISHA. With detailed verification of the BESS simulation, the relative systematic error of detection efficiency derived from the BESS simulation has been determined to be +/-5%, compared with the previous estimation of +/- 15% which was the dominant uncertainty for measurements of cosmic-ray antiproton flux. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(02)00804-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We report new measurements of absolute fluxes of atmospheric unions at mountain altitude. The measurements were carried out with the BESS detector at the top of Mt. Norikura, 2770 m above sea level, in Japan. The overall errors were less than 10%. The measured results are discussed in comparison with theoretical calculations. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0370-2693(02)02265-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

An extremely thin superconducting solenoid magnet is being developed to investigate cosmic-ray antiparticle in the Universe. The uniform solenoidal field is provided in a particle detector system to analyze the particle momentum. The solenoid coil is wound with advanced aluminum stabilized superconductor recently developed by using micro-alloying with Ni, followed by cold-work mechanical hardening. It is designed with a central magnetic field of 1.2 T in a volume of 0.9 m in diameter and 1.4 m in length, the radiation thickness of the coil is to be 0.056 X-o with a physical coil thickness of 3.4 mm. This paper describes the conceptual design and progress of the basic development work.

DOI： 10.1109/TASC.2002.1018438

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The energy spectra of cosmic-ray low-energy antiprotons ((p) over bar 's) and protons (p's) have been measured by BESS in 1999 and 2000, during a period covering reversal at the solar magnetic field. Based an these measurements, a sudden increase of the (p) over bar /p flux ratio following the solar magnetic field reversal was observed, and it generally agrees with a drift model of the solar modulation.

DOI： 10.1103/PhysRevLett.88.051101

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The cosmic-ray hydrogen and helium spectra have been measured by the Balloon Borne Experiment with a Superconducting Solenoid Spectrometer (BESS), which has been flown from Lynn Lake, Manitoba, Canada, annually since 1993. The BESS experiment provides excellent rigidity measurement and precise particle identification with a large geometric acceptance. We present here the hydrogen and helium nuclei energy spectra from 0.2 to 10 GeV nucleon(-1) and their isotopic composition from 0.2 to about 1 GeV nucleon(-1) for the first BESS flight. This provides the first simultaneous measurements of the cosmic-ray secondaries, deuterons, and He-3, with their primaries, protons, and He-4 over this energy range in a period of solar minimum. In this paper, we have achieved significant improvements in data analysis in the following aspects. First, the latest available cross-section data and their parameterizations were utilized in the simulation code developed for this study. Second, a complete simulation was performed for both protons and heavy ions : the delta-ray effect was properly simulated and showed a large influence on the measurement of heavy ions at high energies. Third, the secondary particle correction, which dominates the systematic uncertainty at low energies for singly charged particles, protons and deuterons, was calculated iteratively with the simultaneously measured primary cosmic-ray spectra. In general, the results of this experiment are consistent with other recent measurements using balloon-borne or satellite experiments, but with better precision. The measured spectra of protons, deuterons, 3He, and 4He and their corresponding ratios are compared with different interstellar/heliospheric propagation calculations, which were derived to fit observations of heavy nuclei. The overall good agreement indicates that the propagation history for light cosmic-ray elements, protons, deuterons, and helium nuclei is similar to that of the heavy nuclei. The H-2/H-1 ratio is sensitive to the propagation models, and our results show a tendency of better agreement with the reacceleration model than the standard leaky-box model.

DOI： 10.1086/324140

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The Balloon-borne Experiment with a Superconducting Spectrometer, BESS, aims to study elementary particle/antiparticle phenomena in the early history of the Universe. The instrument has a unique feature of a thin superconducting solenoid magnet enabling a large geometrical acceptance with a horizontally cylindrical configuration. Seven balloon flights have been successfully carried out since 1993. More than 10(3) comic-ray antiproton have been unambiguously detected, and the energy spectrum has been measured with the characteristic peak at 2 GeV. The search for cosmic-ray antihelium brought the upper-limit of the antiheliuni/helium ratio down to < 10(-6). To extend the highly sensitive measurements, we are planning polar long duration flights in Antarctica focusing on the very low energy antiproton spectrum towards the solar-minimum in the next decade. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0273-1177(02)00541-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The energy spectrum of cosmic-ray antiprotons (p's) has been measured by BESS successively in 1993, 1995, 1997 and 1998. In total, 848 (p) over bar 's were clearly identified in energy range 0.18-4.20 GeV. From these successive measurements of the (p) over bar spectrum at various solar activity, we discuss about the effect of the solar modulation and the origin of cosmic-ray (p) over bar 's. The (p) over bar /p ratios showed no distinctive year-to-year variation during the positive Sun's polarity phase. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0927-6505(01)00107-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The BESS spectrometer has measured the energy spectrum of cosmic-ray antiprotons successively in 1993, 1995, 1997 and 1998. In total, 848 antiprotons were clearly identified in energy range 0.18 to 4.20 GeV based on magnetic-rigidity, time-of-flight, energy loss, and Cherenkov radiation measurements. The measured antiproton spectra and antiproton/proton ratios were nearly identical at the upper end of the instrumental energy range, which is consistent with theoretical calculations. In the low energy region. our data show variations that are somewhat larger than expected. This might be due to statistical fluctuation, or might suggest a contribution of primary antiprotons from novel sources. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0273-1177(01)00129-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Recent progress in experimental observations and theoretical investigations of cosmic-ray antiprotons (P's) have brought new light on their origin. The (p) over bar energy spectrum measured by the recent BESS experiment shows the characteristic peak around 2 GeV, which was expected from "secondary" (p) over bar 's, i.e., produced in cosmic-ray interactions with the interstellar gas. The MASS and CAPRICE experiments have detected p's in the higher energy range and show that the flux decreases beyond the peak. These new data are well reproduced by theoretical calculations recently developed. Further sensitive observations with still higher statistics are required to investigate the propagation and solar modulation models in detail and to search for the primary (p) over bar component from novel sources, e.g. evaporating black holes or annihilating neutralino dark matter. In the case of antinuclei searches, an upper limit of a level of 10(-6) is obtained for the antihelium/helium ratio both from the BESS balloon flight and the AXIS space mission. In the future, BESS-polar and AMS on the ISS (International Space Station) may be expected to reach upper limits of 10(-7) and 10(-8), respectively. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0273-1177(01)00111-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A series of Balloon-borne Experiments with a Superconducting Spectrometer, BESS, has been made since 1993. We report here the absolute cosmic-ray proton and helium spectra in energy ranges of 1 to 120 GeV and I to 54 GeV/nucleon, respectively, as measured by the 1998 balloon flight of the BESS spectrometer. Those spectra were determined within overall uncertainties of +/-5 % for protons and +/- 10 % for helium nuclei including statistical and systematic errors. The covered energy range is relevant to the atmospheric neutrinos observed as "fully contained events" in Super-Kamiokande. In order to extend the energy range up to around I TeV, we have started to design and develop new tracking detectors. Those energy spectra in a higher energy region will help to estimate the interstellar spectra of primary cosmic rays and the absolute fluxes of "up-going muons." (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0273-1177(01)00118-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The absolute fluxes of the cosmic-ray antiproton are measured at solar minimum in the energy range 0.2 to 3.2 GeV, based on 460 antiprotons unambiguously detected by BESS spectrometer during its '95 and '97 balloon flights from Lynn Lake, Canada. In the resultant antiproton spectrum we have detected a clear peak around 2 GeV and measured its flux to 10% accuracy. The position and the absolute flux of the peak agree with the prediction of the Standard Leaky Box model for the "secondary" antiprotons. At low energies below I GeV, we observe an excess antiproton flux over the simple Standard Leaky Box prediction. This might indicate that the propagation mechanism needs to be modified, or might suggest a contribution of low-energy antiproton component from novel sources such as evaporating primordial black holes or the annihilating neutralino dark matter. Data from '98 and future Rights are expected to help us to clarify the situation. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have obtained the absolute spectra of H and He by analyzing data collected by a series of annual flights of the Balloon borne Experiment with a Superconducting solenoid Spectrometer payload. This instrument is configured with a cylindrical magnet, a Time-of-Flight system, a set of cylindrical multiwire drift chambers inside and outside the magnet, and a central tracking device Jet chamber. The analysis involves Monte Carlo simulations of the effective geometry factor, studies of various efficiencies, and corrections for the ionization energy loss, attenuation and atmospheric secondaries. Variations of the H and He fluxes at different levels of solar modulation are presented. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

We report cosmic-ray proton and helium spectra in energy ranges of 1-120 GeV nucleon(-1) and 1-54 GeV nucleon(-1), respectively, measured by a flight of the Balloon-borne Experiment with Superconducting Spectrometer (BESS) in 1998. The magnetic rigidity of the cosmic ray was reliably determined by highly precise measurement of the circular track in a uniform solenoidal magnetic field of 1 T. Those spectra were determined within overall uncertainties of +/-5% for protons and +/- 10% for helium nuclei including statistical and systematic errors.

DOI： 10.1086/317873

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We describe the design and performance of a large-area scintillator hodoscope onboard the BESS rigidity spectrometer; an instrument with an acceptance of 0.3 m(2) sr. The hodoscope is configured such that 10 and 12 counters are, respectively, situated in upper and lower layers. Each counter is viewed from its ends by 2.5 in, fine-mesh photomultiplier tubes placed in a stray magnetic field of 0.2 T. Various beam-test data are presented. Use of cosmic-ray muons at ground-level confirmed 50 ps timing resolution for each layer, giving an overall time-of-fight resolution of 70 ps rms using a pure Gaussian-resolution function. Comparison with previous measurements on a similar scintillator hodoscope indicates good agreement with the scaling law that timing resolution is proportional to 1/rootN(pe), where N-pe is the effective number of photoelectrons. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(00)00571-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The BESS detector is a new type of balloon-borne spectrometer which utilizes various technologies recently developed for collider experiments. The principal scientific objectives include a measurement of cosmic-ray antiproton spectrum, search for anti-nuclei in cosmic radiation, and precise meaurements of cosmic-ray primaries. A thin superconducting solenoidal coil produces a uniform magnetic field of 1 T. Cylindrical drift chambers are located inside and outside the coil and perform continuous tracking. The momentum resolution is 0.5% at 1 GeV/c. i.e., the maximum detectable rigidity is 200 GV. Scintillation counter hodoscopes, placed above and below the solenoid, provide timing and dE/dx measurements and trigger generation. The timing resolution is 80 ps/counter. This cylindrical configuration achieves a large geometrical acceptance of 0.35 m(2) sr which is essential to detect rare cosmic-ray particles. In order to cope with high trigger rate and large data size, intelligent trigger circuits and a fast and parallel data acquision system are also developed. In 1993, the first scientific flight of the BESS apparatus was carried out and the first mass-measured antiprotons were detected at energies below 500 MeV (C) 2000 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

The energy spectrum of cosmic-ray antiprotons ((p) over bar's) has been measured in the range 0.18-3.56 GeV, based on 458 (p) over bar's collected by BESS in a recent solar-minimum period. We have detected for the first time a characteristic peak at 2 GeV of (p) over bar's originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS data with still higher statistics will allow us to study the solar modulation and the propagation in detail and to search for primary (p) over bar components.

DOI： 10.1103/PhysRevLett.84.1078

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

The absolute fluxes of the cosmic-ray antiprotons at solar minimum are measured in the energy range 0.18 to 1.4 GeV, based on 43 events unambiguously detected in BESS 1995 data. The resultant energy spectrum appears to be flat below 1 GeV, compatible with a possible admixture of primary antiproton component with a soft energy spectrum, while the possibility of secondary antiprotons alone explaining the data cannot be excluded with the present accuracy. Further improvement of statistical accuracy and extension of the energy range are planned in future BESS flights. [S0031-9007(98)07573-5].

DOI： 10.1103/PhysRevLett.81.4052

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This paper describes the development of a threshold-type aerogel Cherenkov counter with a large sensitive area of 0.6 m(2) to be carried onboard the BESS rigidity spectrometer to detect cosmic-my antiprotons. The design incorporates a large diffusion box containing 46 finemesh photomultipliers, with special attention being paid to achieving good performance under a magnetic field and providing sufficient endurance while minimizing material usage. The refractive index of the aerogel was chosen to be 1.03. By utilizing the muons and protons accumulated during the cosmic-ray measurements at sea level, a rejection factor of 10(4) was obtained against muons with beta approximate to 1, while keeping 97% efficiency for protons below the threshold. (C) 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-9002(98)00772-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A very sensitive search for cosmic-ray antihelium was performed using data obtained from three scientific flights of the BESS magnetic rigidity spectrometer. We have not observed any antihelium; this places a model-independent upper limit (95% C.L.) on the antihelium flux of 6 x 10(-4) m(-2)sr(-1)s(-1) at the top of the atmosphere in the rigidity region 1 to 16 GV, after correcting for the estimated interaction loss of antihelium in the air and in the instrument. The corresponding upper limit on the <(He)over bar>/He flux ratio is 3.1 x 10(-6), 30 times more stringent than the limits obtained in similar rigidity regions with magnetic spectrometers previous to BESS. (C) 1998 Published by Elsevier Science B.V.

DOI： 10.1016/S0370-2693(98)00131-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A positioning of the neutrino detector SuperKamiokande (SK) was made for a long-baseline neutrino oscillation experiment planned at KEK. For positioning, Global Positioning System (GPS) was employed. It has been demonstrated that GPS is of practical use for measuring the positions of SK and ECEK, being 250km distance from each other, to a better resolution. The geodetic coordinates at the SK center were obtained to be Lat. 36 degrees 25'32.5862 '' N., Long. 137 degrees 18'37.1241 '' E., H. 371.839 m in the global ellipsoidal coordinate system, WGS-84. The obtained coordinates are based on the coordinates given at a triangulation point at the KEK site. The present work will be fed back for constructing the neutrino beam line.

DOI： 10.1016/S0168-9002(97)00899-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

We have searched for antihelium in the galactic cosmic rays using data obtained on the flight of the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) launched from Lynn Lake, Manitoba, in northern Canada on 1995 July 25. The balloon reached an altitude of 36.5 km with a residual overburden of 5 g cm(-2). The total observation time was 12.2 kr with a live-time fraction of 0.61. No antihelium was observed after selections based on dE/dx and event quality cuts at rigidities between 1.6 and 16 GV/c; we infer that 536,420 helium nuclei survived the same cuts. This result leads to an upper limit to the <(He)over bar>/He abundance ratio of 8.1 x 10(-6) (95% confidence level), a factor of 2.7 over the lowest previous limit. Because this limit is for the first time at the level where predicted limits become astrophysically interesting (Ahlen et al.), we have reexamined the transport of cosmic rays in intergalactic space. We show that little can be learned about distant (> 10 Mpc) domains of antimatter from a null result.

DOI： 10.1086/310700

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

We have studied the low-energy antiprotons in the cosmic rays by utilizing data obtained by the Balloon-borne Experiment with a Superconducting magnetic rigidity Spectrometer (BESS) flown in 1993 July from Lynn Lake, Manitoba, Canada. A detailed description of the event selection criteria and back-ground corrections is given. Seven antiprotons are found that give an antiproton flux of 6.4(-3.5)(+5.5) x 10(-3)(m(2) sr s GeV)(-1) and an antiproton/proton ratio of 5.2(-2.8)(+4.4) x 10(-6) in the 200-600 MeV energy range. These results are consistent with a secondary origin of low-energy cosmic-ray antiprotons within our uncertainties, but they still require the precise measurement of the spectrum shape below 500 MeV to clarify exactly the model of particle propagation and possible contributions from exotic sources.

DOI： 10.1086/303463

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

The Balloon Bome Experiment with a Superconducting Solenoid Spectrometer (BESS) was flown annually in 1993, 1994, and 1995. In this report we present the energy spectra and isotopic composition of cosmic ray H and He measured from the 1993 flight. The low energy fluxes of H and He agree with the IMP-8 satellite data for a 26 day period (7/14/93 - 8/9/93) that overlapped the BESS flight. Both H-2 and He-3 were well separated from H-1 and He-4. The measured spectra were corrected for the atmospheric overburden and compared with the interstellar/heliospheric propagation calculations. (C) 1997 COSPAR.

DOI： 10.1016/S0273-1177(96)00140-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

Balloon-borne experiment using a superconducting spectrometer were carried out successfully in northern Canada, in summer 1993 to 1995. In `93 flight, seven antiprotons were detected in the kinetic range between cen 200 and 600 MeV. The corresponding cosmic ray antiproton flux at the top of the atmosphere is fond to be 6.4(-3.5)(+5.5) x 10(-3)(m(2) sr s GeV)(-1). In '95 flight. improvement on the TOF resolution resulted to the observation of the forty antiprotons in the kinetic energy region 175 MeV to 1.3 GeV. The analysis on '95 flight is under way. (C) 1997 COSPAR.

DOI： 10.1016/S0273-1177(96)00145-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

A new technique has been used to determine a limit on the nu tau mass using Z(0) --&gt; tau(+)tau(-) events selected from 140 pb(-1) of data collected with the OPAL detector at LEP during the period 1990-1994. Using Z(0) --&gt; tau(+)tau(-) events in which both tau-leptons decay to three charged particles, a novel likelihood analysis is applied to the 2-dimensional distribution of missing mass squared and missing energy, from which we obtain a limit of M nu(tau) &lt; 35.3 MeV at 95% confidence level. Combining our new result with OPAL's previous published measurement from tau --&gt; 5 pi nu(tau) decays, we obtain the new 95% confidence level limit of M nu(tau) &lt; 29.9 MeV.

DOI： 10.1007/s002880050240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Cross-sections and angular distributions for the production of events with single and multiple photons are measured from data recorded with the OPAL detector at the recently upgraded LEP collider. The measured cross-sections are generally consistent with Standard Model expectations for the e(+)e(-) --> <nu(nu)over bar gamma(gamma)> and e(+)e(-) --> gamma gamma(gamma) processes. Six events with an acoplanar photon pair and large missing mass are found. The observed number of events is larger than expected from e(+)e(-) --> <nu(nu)over bar gamma gamma>; however, the missing mass distribution is compatible with the Z(0) resonance. Deviations from QED are constrained by the data on e(+)e(-) --> gamma gamma(gamma). Lower limits are set at 95% confidence level on the QED cut-off parameters Lambda(+) and Lambda(-) of 152 GeV and 142 GeV, respectively, and also on the mass of an excited electron of 147 GeV.

DOI： 10.1016/0370-2693(96)00488-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A search for scalar particles and neutralinos such as those predicted by supersymmetric models has been performed using a data sample of 4.4 million hadronic Z(0) decays recorded by the OPAL detector at the e(+)e(-) collider LEP. The production of such particles typically leads to event topologies consisting of an acoplanar pair of jets, or of a mono-jet, accompanied by sizeable missing energy owing to neutrinos and other undetectable neutral particles. Limits are obtained, at the 95% confidence level, on the masses and production rates of scalar particles produced in association with the Z(0). Limits are also placed on neutralino production, for which an additional possible signature is also studied, events containing a single observed photon. Within the Minimal Supersymmetric Standard Model, the mass of the lightest neutralino is found to be larger than 12.5 GeV/c(2) at 95% C.L., provided that tan beta is larger than 1.5.

DOI： 10.1016/0370-2693(96)00502-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A search for charginos and neutralinos, predicted by supersymmetric theories, has been performed using a data sample of 2.6 pb(-1) at a centre-of-mass energy of root s = 130 GeV and 2.6 pb(-1) at 136 GeV collected with the OPAL detector at LEP during November 1995. No candidate events were observed. The 95% C.L. lower limit on the lightest chargino mass in the Minimal Supersymmetric Standard Model is 65.4 GeV if the universal scalar mass m(o) is greater than 1 TeV, and 58.7 GeV for the smallest m(o) compatible with slepton and sneutrino mass limits obtained at centre-of-mass energies near the Z peak. These limits were obtained under the conditions that the lightest chargino is heavier than the lightest neutralino by more than 10 GeV and tan beta is larger than 1.5. The results of a model independent search for charginos and neutralinos are also given.

DOI： 10.1016/0370-2693(96)00301-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER VERLAG  

A search for the hadronic decay of a hypothetical resonance S-0 in the process e(+)e(-) --&gt; gamma + hadrons at Z(0) energies is reported. Particular care is taken to optimise the sensitivity to a scalar resonance decaying into bottom quarks, as expected for Higgs production, e(+)e(-) --&gt; Z(0) --&gt; H-0 gamma with H-0 --&gt; b (b) over bar, in the Standard Model or some of its extensions. No evidence for such a resonance is observed in a sample of about 5 million produced Z(0)'s. The results are interpreted in terms of models of non-standard Higgs production. An update of a search for a resonance produced in association with hadrons and the subsequent resonance decay into two photons is also presented.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A new measurement of the tau lifetime is presented. It uses data collected with the OPAL detector during 1994, which almost doubles the size of the OPAL tau sample. Two statistically independent techniques are used: an impact parameter analysis of one-prong decay tracks and a fit to the decay length distribution of three-prong decays. The lifetime obtained from the 1994 data by combining the results of these methods is tau(tau) = 289.7 +/- 2.5(stat) +/- 1.5(sys) fs. When combined with the previous OPAL tau lifetime measurement the improved tau lifetime is tau(tau) = 289.2 +/- 1.7(stat.) +/- 1.2(sys.) fs.

DOI： 10.1016/0370-2693(96)00255-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A search for l(+)l(-) <q(q)over bar> (l = e, mu) four-fermion final states in high multiplicity events has been performed at root s approximate to m(z) and above the Z peak at root s = 130 GeV and root s = 136 GeV, The data taken with OPAL correspond to an integrated luminosity of 132.4 pb(-1) and 5.3 pb(-1) at root s approximate to m(z) and root s = 130-136 GeV, respectively. While at the Z resonance the data are in good agreement with the Standard Model predictions, we find more events than expected at root s = 130-136 GeV, especially in the mu(+)mu(-) <q(q)over bar> channel, where 5 events remain after all cuts, with only 0.6 predicted by the Monte Carlo simulation. For all center-of-mass energies the observed shapes of the differential distributions are consistent with the predictions.

DOI： 10.1016/0370-2693(96)00397-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Production of events with multihadronic and leptonic final states has been measured in e(+)e(-) collisions at centre-of-mass mass energies significantly above the Z(0) mass, using the OPAL detector at LEP. A substantial production rate of radiative Z(0) gamma events was observed, as expected, together with events with less energetic initial-state photons, The cross-sections and leptonic forward-backward asymmetries were measured and compared with Standard Model expectations, In a model-independent fit to the Z(0) lineshape, the hadronic cross-section and lepton asymmetries presented here provide constraints on the size of the gamma Z(0)-interference term which are complementary to those afforded by LEP data accumulated at the Z(0) resonance.

DOI： 10.1016/0370-2693(96)00394-2

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：C E R N  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

A balloon-borne experiment using a superconducting solenoidal magnet spectrometer is being carried out with aims at making a precise measurement of low energy antiproton flux in cosmic rays and a highly sensitive search for primordial antimatter in the Universe. The spectrometer has a unique cylindrical configuration associated with a thin superconducting solenoidal magnet and is realizing a geometrical acceptance of 0.5 m(2)sr. The first scientific ballooning flight was successfully carried out in northern Canada, in summer, 1993, and the second flight is being prepared to he carried out in summer, 1994. Performance of the spectrometer in the first night and progress of the experiment are described.

DOI： 10.1016/0273-1177(95)00684-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

A search for cosmic-ray antiprotons was performed using a balloon-borne experiment with a superconducting magnetic rigidity spectrometer (BESS). We have detected four antiprotons in the kinetic energy range between 300 and 500 MeV, the first antiprotons to be identified by a direct mass measurement. The corresponding (p) over bar/p flux ratio at the top of the atmosphere is found to be 1.2(-0.65)(+1.0) X 10(-5). No antiprotons were observed in the range between 175 and 300 MeV, resulting in a 90% C.L. upper limit on the flux ratio of 2.9 X 10(-5).

DOI： 10.1103/PhysRevLett.75.3792

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A thin superconducting solenoid was launched by using a large balloon up to an altitude of 36.5 km in Northern Canada in the summer of 1993 as a core facility for the cosmic ray spectrometer, BESS. The magnet was excited up to 1.0 T in persistent current mode on the ground and was launched being attended with 2.7 G shocks. After 17 hours successful flight, it was discharged on the sky and made a mild descending and landing by using a parachute for recovery. The magnet was safely operated without problems during flight in 1993 and contributed to an second observation in the summer of 1994.

DOI： 10.1109/77.402634

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ARGALIA EDITORE DELLE ARTI GRAFICHE EDITORIALI SRL  

BESS (balloon-borne Experiment with Superconducting Solenoid) is an omni-purpose spectrometer for cosmic ray measurements with a large geometrical acceptance of 0.3 m(2)sr and a high maximum detectable momentum of 200 GeV/c. The design principle and the performance of the detector will be presented based on the flight data in '93 and '94.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ARGALIA EDITORE DELLE ARTI GRAFICHE EDITORIALI SRL  

The cosmic ray H and He spectra have been measured from the 1993 balloon flight of the BESS spectrometer, which was launched from Lynn Lake, Manitoba, Canada on July 26, 1993 and spent 18 hrs at float altitude. The maximum detectable rigidity is estimated to be 200 GV. The measured spectra show an instrumental cutoff at similar to 170 MeV/n (0.6 GV for protons) which was apparently higher than the local geomagnetic cutoffs (0.38 - 0.56 GV) along the balloon trajectory. With the preliminary proton and helium spectra obtained from about 5% of the flight data, the solar modulation parameter for BESS-93 is estimated to be 700 +/- 100 MV.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ARGALIA EDITORE DELLE ARTI GRAFICHE EDITORIALI SRL  

A search for cosmic-ray antiprotons was performed using a Balloon-borne Experiment with a Superconducting magnetic rigidity Spectrometer (BESS). We have detected four antiprotons in the kinetic energy range between 300 and 500 MeV, the lowest energy cosmic-ray antiprotons ever observed. The corresponding <(p)over bar /p> flux ratio at the top of the atmosphere is found to be 1.2 +/- 0.7 x 10(-5). No antiprotons were observed in the range between 175 and 300 MeV, resulting in a 90% C.L. upper limit on the flux ratio of 2.4 x 10(-5).

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A remote console system is developed to improve remote control over experimental apparatus borne on the balloon. The remote console system, residing at a ground station for balloon borne experiments, sends commands to the apparatus and receives transmissions from it. The system communicates by radio with microcomputers incorporated in the experimental apparatus borne. on a balloon, where the microcomputers control the apparatus individually. The system includes plural personal computers and work stations which share the transmissions from the apparatus. The transmissions from the apparatus are formatted in a bit oriented protocol, which dispenses with a formatter and facilitate interface with the personal computers. The article describes the implementation of the system and the communication between the ground station and the balloon-borne apparatus.

DOI： 10.1109/23.256683

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：UNIV CALGARY PR  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In a balloon-borne experiment, signals from detectors are processed in a balloon-borne apparatus so as to fit the data bandwidth of storage devices installed in the apparatus. The process begins at front-end processors receiving signals from detectors and proceeds under successive stages by dedicated processors. Event data are finally fed to a computer bank where the events are further selected before being written into the storage devices. The computer bank is made of transputer modules. The transputers are widely employed and some processors are implemented by the transputers. In the article, how the processors are integrated is described together with function and implementation of the individual processors.

DOI： 10.1109/23.173212

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PERGAMON PRESS LTD  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

DOI： 10.1109/NSSMIC.1991.259109

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.74.1.0_2590

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.70.2.0_2512

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：Japan Aerospace Exploration Agency  

The energy spectrum of cosmic-ray antiprotons has been measured by BESS successively in 1993, 1995, 1997, 1998, 1999 and 2000. In total more than 2 x10^3 antiprotons were clearly identified in an energy range of 0.18 to 4.20 GeV. From these successive measurements of the antiproton spectrum at various solar activity, the effect of the solar modulation and the origin of cosmic-ray antiprotons are discussed.

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Other Link： http://repository.tksc.jaxa.jp/pl/dr/IS0200098000

Language：Japanese   Publisher：Japan Aerospace Exploration Agency  

A long-duration balloon flight in Antarctica, BESS-Polar experiment, is being prepared. It aims at extremely sensitive measurement of low energy antiprotons to search for any novel primary origin and to study the cosmic-ray propagation and the solar modulation. The search for cosmic antimatter such as anti-helium is a fundamental objective to study baryon asymmetry / symmetry in the Universe. This report describes the progress and future prospect of BESS-Polar experiment.

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Other Link： http://repository.tksc.jaxa.jp/pl/dr/IS0200099000

Language：English   Publisher：UNIV CHICAGO PRESS  

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Language：Japanese   Publisher：Japan Aerospace Exploration Agency  

Search for cosmic-origin anti-particle were performed using Balloon-borne Experiment with a Superconducting magnetic rigidity Spectrometer (BESS). Based on the data took in '93 flight, we set a 95% C. L upper limit of 4.4×10^<-5> on Anti-He/He flux ratio. We have detected four antiproton in the kinetic energy range between 300 an 500MeV, corresponding to the antiproton/proton flux ratio of 1.2×10^<-5>.

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Other Link： http://hdl.handle.net/10097/50952

Language：Japanese   Publisher：Japan Aerospace Exploration Agency  

Balloon-borne Experiment using a superconducting magnetic rigidity spectromeer is being carried out as a NASA-ISAS cooperative project. The spectrometer features to have a large geometrical acceptance of 0.4 m^2str based on a concept of transparent solenoidal magnet and horizontally cylindrical layout of the spectrometer, and it may realize a highly sensitive search for cosmic ray antiparticle search. This paper describes the spectrometer and progress of the balloon-borne spectrometer as the part (1).

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：PERGAMON PRESS LTD  

A balloon-borne superconducting solenoidal magnet spectrometer, BESS, has been designed and developed to investigate cosmic-rays and particle-astrophysics. Search for primordial antimatter in cosmic-rays and observation of gamma-rays are primary objectives to study early history of the Universe. The cylindrical spectrometer configuration with a thin superconducting solenoid magnet is optimized to provide a large geometrical acceptance of 0.5-1.0 m(2)sr for these scientific objectives. The spectrometer system has been completed and is planned to be launched for the first scientific flight from Lynn Lake, Canada, in 1993. This report describes the progress of the spectrometer development and discuss about its capability to search for primordial antimatter in cosmic rays.

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Language：English   Publisher：ELSEVIER SCI LTD  

A Balloon Experiment with Superconducting Spectrometer (BESS) to search for primordial anti-matter abundance in cosmic radiation and to measure anti-proton spectrum is being prepared. A large geometry factor of 1.2 m2sr was achieved by the solenoidal detector configuration. The magnet provides an uniform magnetic field of 1.2 tesla over a cylindrical volume of 0.85m in diameter and 1.0m in length. Anti-helium nuclei will be searched for to a level of anti-He/He is similar to 10(-8) and the low energy primary anti-proton flux will be observed down to anti-proton/proton is similar to 10(-6). The superconducting magnet has been constructed and excited to 1 tesla and showed good and stable performance. The main tracking device, jet type drift chamber, together with the readout electronics and data acquisition system have been assembled and tested. A flight to test the detector performance at the balloon altitude was successfully carried out in September 1989.

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