掲載種別：研究論文（学術雑誌）  

The JSNS^2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment aims to search for oscillations involving a sterile neutrino
in the eV^2 mass-splitting range. The experiment will search for the appearance
of electron antineutrinos oscillated from muon antineutrinos. The electron
antineutrinos are detected via the inverse beta decay process using a liquid
scintillator detector. A 1MW beam of 3 GeV protons incident on a spallation
neutron target produces an intense and pulsed neutrino source from pion, muon,
and kaon decay at rest. The JSNS^2 detector is located 24 m away from the
neutrino source and began operation from June 2020. The detector contains 17
tonnes of gadolinium (Gd) loaded liquid scintillator (LS) in an acrylic vessel,
as a neutrino target. It is surrounded by 31 tonnes of unloaded LS in a
stainless steel tank. Optical photons produced in LS are viewed by 120 R7081
Hamamatsu 10-inch Photomultiplier Tubes (PMTs). In this paper, we describe the
JSNS^2 detector design, construction, and operation.

DOI： 10.1016/j.nima.2021.165742

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arXiv

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その他リンク： http://arxiv.org/pdf/2104.13169v2

This article describes the goal and expected sensitivity of the JSNS$^2$-II
experiment at J-PARC Materials and Life Science Experimental Facility (MLF).
The JSNS$^2$-II experiment is the second phase of the JSNS$^2$ experiment
(J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) with two
detectors which are located in 24 m (an existing detector) and 48 m (new one)
baselines to improve the sensitivity of the search for sterile neutrinos,
especially in the low $\Delta m^2$ region, which has been indicated by the
global fit of the appearance mode. The new second detector has a similar
structure as the existing JSNS$^2$ detector, which is already working. To
compensate for the reduction of the neutrino flux due to the distance from the
mercury target, the target mass of the Gd-loaded liquid scintillator which is
the Linear AlkylBenzene (LAB) based liquid scintillator inside the acrylic
vessel is 35 tons. To keep the same photo-coverage of the detector as the first
detector, we will surround the acrylic vessel with 240 PMTs. With this
experimental setup and 5 years (times 1 MW beam power) exposure, the
sensitivity of the JSNS$^2$-II is significantly improved compared to the
current JSNS$^2$, especially in the low $\Delta m^2$ oscillation parameter
region. The JSNS$^2$-II can also confirm or refute the most of the oscillation
parameters' space preferred by the previous experiments with 3 sigma C.L..
Considering these situations and world wide status of the sterile neutrino
searches, we are eager to start the data taking with the two detector
configuration from 2023. The fund to build the second detector was already
secured.

arXiv

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その他リンク： http://arxiv.org/pdf/2012.10807v1

掲載種別：研究論文（学術雑誌）  

The JSNS$^{2}$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment aims to search for neutrino oscillations over a 24 m short
baseline at J-PARC. The JSNS$^{2}$ inner detector is filled with 17 tons of
gadolinium(Gd)-loaded liquid scintillator (LS) with an additional 31 tons of
unloaded LS in the intermediate $\gamma$-catcher and an optically separated
outer veto volumes. A total of 120 10-inch photomultiplier tubes observe the
scintillating optical photons and each analog waveform is stored with the flash
analog-to-digital converters. We present details of the data acquisition,
processing, and data quality monitoring system. We also present two different
trigger logics which are developed for the beam and self-trigger.

DOI： 10.1088/1748-0221/15/09/T09002

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arXiv

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その他リンク： http://arxiv.org/pdf/2006.00670v1

掲載種別：研究論文（学術雑誌）  

The JSNS$^2$ experiment is aimed to search for sterile neutrino oscillations
using a neutrino beam from muon decays at rest. The JSNS$^2$ detector contains
17 tons of 0.1\% gadolinium (Gd) loaded liquid scintillator (LS) as a neutrino
target. Detector construction was completed in the spring of 2020. A slow
control and monitoring system (SCMS) was implemented for reliable control and
quick monitoring of the detector operational status and environmental
conditions. It issues an alarm if any of the monitored parameters exceed a
preset acceptable range. The SCMS monitors the high voltage (HV) of the
photomultiplier tubes (PMTs), the LS level in the detector, possible LS
overflow and leakage, the temperature and air pressure in the detector, the
humidity of the experimental hall, and the LS flow rate during filling and
extraction. An initial 10 days of data-taking with a neutrino beam was done
following a successful commissioning of the detector and SCMS in June 2020. In
this paper, we present a description of the assembly and installation of the
SCMS and its performance.

DOI： 10.1093/ptep/ptab044

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arXiv

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その他リンク： http://arxiv.org/pdf/2005.01286v4

掲載種別：研究論文（学術雑誌）  

The JSNS$^{2}$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment aims to search for neutrino oscillations over a 24\,m short
baseline at J-PARC. The JSNS$^{2}$ inner detector is filled with 17 tons of
gadolinium-loaded liquid scintillator (LS) and both the intermediate
$\gamma$-catcher and the optically separated outer veto are filled with
un-loaded LS. Optical photons from scintillation are observed by 120
Photomultiplier Tubes (PMTs). A total of 130 PMTs for the JSNS2 experiment were
both donated by other experiments and purchased from Hamamatsu. Donated PMTs
were purchased around 10 years ago, therefore JSNS$^{2}$ did pre-calibration of
the PMTs including the purchased PMTs. 123 PMTs demonstrated acceptable
performance for the JSNS$^{2}$ experiment, and 120 PMTs were installed in the
detector.

DOI： 10.1088/1748-0221/15/07/T07003

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arXiv

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その他リンク： http://arxiv.org/pdf/2005.01599v2

掲載種別：研究論文（学術雑誌）  

The JSNS$^{2}$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment will search for neutrino oscillations over a 24 m short
baseline at J-PARC. The JSNS$^{2}$ inner detector will be filled with 17 tons
of gadolinium-loaded liquid scintillator (LS) with an additional 31 tons of
unloaded LS in the intermediate $\gamma$-catcher and outer veto volumes.
JSNS$^{2}$ has chosen Linear Alkyl Benzene (LAB) as an organic solvent because
of its chemical properties. The unloaded LS was produced at a refurbished
facility, originally used for scintillator production by the RENO experiment.
JSNS$^{2}$ plans to use ISO tanks for the storage and transportation of the LS.
In this paper, we describe the LS production, and present measurements of its
optical properties and long term stability. Our measurements show that storing
the LS in ISO tanks does not result in degradation of its optical properties.

DOI： 10.1088/1748-0221/14/09/T09010

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arXiv

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その他リンク： http://arxiv.org/pdf/1906.00213v2

掲載種別：研究論文（学術雑誌）  

Stainless steel is a candidate of the inner surface of the storage container
for LAB-based Gadolinium loaded liquid scintillator (Gd-LS) to be used in the
JSNS$^2$ neutrino detector. Aging effect on Gd concentration of Gd-LS was
investigated with the Gd-LS sample stored in the passivated stainless steel
bottle in two independent methods. The direct comparison of the neutron capture
time measurement showed that there is no significant degradation of the capture
time after 602 days aging. Titration was performed to measure Gd concentration,
and the result after 466 days aging is consistent with the result before aging
within the uncertainty of the measurement. The upper limit of degradation of Gd
concentration in 21 kL tank case is estimated as 0.5 % for 10 years of storage.
Both results lead to a conclusion that stainless steel is usable for Gd-LS
storage for JSNS$^2$ experiment.

DOI： 10.1088/1748-0221/14/09/P09007

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arXiv

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その他リンク： http://arxiv.org/pdf/1904.10243v1

掲載種別：研究論文（学術雑誌）  

This paper describes the design and the construction of the stainless steel
tank of the JSNS$^2$ detector. The leakage was examined using water and gas
after the construction. The new sealing technique with liquid gasket was
developed, and its sealing capability was evaluated quantitatively. The result
shows over 5 times better value than the tolerance level of leakage.The
acceleration measurement during the transportation of the tank shows adequate
robustness.These tests prove that the stainless steel tank is feasible to use
the real experiment.

DOI： 10.1088/1748-0221/14/09/T09001

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arXiv

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その他リンク： http://arxiv.org/pdf/1904.08674v2

In this document, the technical details of the JSNS$^2$ (J-PARC Sterile
Neutrino Search at J-PARC Spallation Neutron Source) experiment are described.
The search for sterile neutrinos is currently one of the hottest topics in
neutrino physics. The JSNS$^2$ experiment aims to search for the existence of
neutrino oscillations with $\Delta m^2$ near 1 eV$^2$ at the J-PARC Materials
and Life Science Experimental Facility (MLF). A 1 MW beam of 3 GeV protons
incident on a spallation neutron target produces an intense neutrino beam from
muon decay at rest. Neutrinos come predominantly from $\mu^+$ decay: $\mu^{+}
\to e^{+} + \bar{\nu}_{\mu} + \nu_{e}$. The experiment will search for
$\bar{\nu}_{\mu}$ to $\bar{\nu}_{e}$ oscillations which are detected by the
inverse beta decay interaction $\bar{\nu}_{e} + p \to e^{+} + n$, followed by
gammas from neutron capture on Gd. The detector has a fiducial volume of 17
tons and is located 24 meters away from the mercury target. JSNS$^2$ offers the
ultimate direct test of the LSND anomaly.
In addition to the sterile neutrino search, the physics program includes
cross section measurements with neutrinos with a few 10's of MeV from muon
decay at rest and with monochromatic 236 MeV neutrinos from kaon decay at rest.
These cross sections are relevant for our understanding of supernova explosions
and nuclear physics.

arXiv

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その他リンク： http://arxiv.org/pdf/1705.08629v1

The JSNS$^2$ (J-PARC E56) experiment aims to search for a sterile neutrino at
the J-PARC Materials and Life Sciences Experimental Facility (MLF). After the
submission of a proposal to the J-PARC PAC, Stage-1 approval was granted to the
JSNS$^2$ experiment on April 2015.This approval followed a series of background
measurements which were performed in 2014.
Recently, funding (the grant-in-aid for scientific research (S)) in Japan for
building one 25~ton fiducial volume detector module was approved for the
experiment. Therefore, we aim to start the experiment with one detector in
JFY2018-2019. We are now working to produce precise cost estimates and schedule
for construction, noting that most of the detector components can be produced
within one year from the date of order. This will be reported at the next PAC
meeting.
In parallel to the detector construction schedule, JSNS$^2$ will submit a
Technical Design report (TDR) to obtain the Stage-2 approval from the J-PARC
PAC.The recent progress of the R$\&$D efforts towards this TDR are shown in
this report. In particular, the R$\&$D status of the liquid scintillator,
cosmic ray veto system, and software are shown.
We have performed a test-experiment using 1.6~L of liquid scintillator at the
3rd floor of the MLF building in order to determine the identities of
non-neutrino background particles coming to this detector location during the
proton bunch. This is the so-called "MLF 2015AU0001" experiment. We briefly
show preliminary results from this test-experiment.

arXiv

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その他リンク： http://arxiv.org/pdf/1610.08186v1