We present the first measurement of the missing energy due to nuclear effects in monoenergetic, muon neutrino charged-current interactions on carbon, originating from K^{+}→μ^{+}ν_{μ} decay at rest (E_{ν_{μ}}=235.5  MeV), performed with the J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source liquid scintillator based experiment. Toward characterizing the neutrino interaction, ostensibly ν_{μ}n→μ^{-}p or ν_{μ}^{12}C→μ^{-}^{12}N, we define the missing energy as the energy transferred to the nucleus (ω) minus the kinetic energy of the outgoing proton(s), E_{m}≡ω-∑T_{p}, and relate this to visible energy in the detector, E_{m}=E_{ν_{μ}}(235.5  MeV)-m_{μ}(105.7  MeV)+[m_{n}-m_{p}(1.3  MeV)]-E_{vis}. The missing energy, which is naively expected to be zero in the absence of nuclear effects (e.g., nucleon separation energy, Fermi momenta, and final-state interactions), is uniquely sensitive to many aspects of the interaction, and has previously been inaccessible with neutrinos. The shape-only, differential cross section measurement reported, based on a (77±3)% pure double-coincidence kaon decay-at-rest signal (621 total events), provides detailed insight into neutrino-nucleus interactions, allowing even the nuclear orbital shell of the struck nucleon to be inferred. The measurement provides an important benchmark for models and event generators at hundreds of MeV neutrino energies, characterized by the difficult-to-model transition region between neutrino-nucleus and neutrino-nucleon scattering, and relevant for applications in nuclear physics, neutrino oscillation measurements, and Type-II supernova studies.

JSNS2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of $\bar{\nu }_{\mu } \rightarrow \bar{\nu }_e$ appearance oscillations using neutrinos from muon decay-at-rest. For this search, rejecting cosmic-ray-induced neutron events by Pulse Shape Discrimination (PSD) is essential because the JSNS2 detector is located above ground, on the third floor of the building. We have achieved 94.95%$\pm$0.15% rejection of neutron events while keeping 92.82%$\pm$1.77% of signal, electron-like events using a data-driven likelihood method. This article will report the PSD technique using the full fiducial volume of the JSNS2 detector.

JSNS$^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of $\bar{\nu}_{\mu} \rightarrow \bar{\nu}_e$ appearance oscillations using neutrinos with muon decay-at-rest. For this search, rejecting cosmic-ray-induced neutron events by Pulse Shape Discrimination (PSD) is essential because the JSNS$^2$ detector is located above ground, on the third floor of the building. We have achieved 95$\%$ rejection of neutron events while keeping 90$\%$ of signal, electron-like events using a data driven likelihood method.

JSNS$^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment which searches for sterile neutrinos via the observation of $\bar{\nu}_{\mu} \to \bar{\nu}_{e}$ appearance oscillations using muon decay-at-rest neutrinos. The data taking of JSNS$^2$ have been performed from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is (9.29$\pm 0.39) \times 10^{-8}$ / spill with 0.75 MW beam power and comparable to the number of searching signals.

Abstract JSNS $$^2$$ 2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that searches for sterile neutrinos via the observation of $$\bar{\nu }_{\mu } \rightarrow \bar{\nu }_{e}$$ ν ¯ μ → ν ¯ e appearance oscillations using muon decay-at-rest neutrinos. The JSNS $$^2$$ 2 experiment performed data taking from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is ( $$9.29\pm 0.39) \times 10^{-8}$$ 9.29 ± 0.39 ) × 10 - 8 /spill with 0.75 MW beam power and comparable to the expected number of signal events.

The JSNS$^{2}$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment designed for the search for sterile neutrinos. The experiment is currently at the stage of the second phase named JSNS$^{2}$-II with two detectors at near and far locations from the neutrino source. One of the key components of the experiment is an acrylic vessel, that is used for the target volume for the detection of the anti-neutrinos. The specifications, design, and measured properties of the acrylic vessel are described.

Liquid detectors; Neutrino detectors

We report the measured production rates of unstable isotopes ^9Li and ^8He produced by cosmic muon spallation on ^12C using two identical detectors of the RENO experiment. Their beta-decays accompanied by a neutron make a significant contribution to backgrounds of reactor antineutrino events in precise determination of the smallest neutrino mixing angle. The mean muon energy of its near (far) detector with an overburden of 120 (450) m.w.e. is estimated as 33.1 +- 2.3 (73.6 +- 4.4) GeV. Based on roughly 3100 days of data, the cosmogenic production rate of ^9Li (^8He) isotope is measured to be 44.2 +- 3.1 (10.6 +- 7.4) per day at near detector and 10.0 +- 1.1 (2.1 +- 1.5) per day at far detector. This corresponds to yields of ^9Li (^8He), 4.80 +- 0.36 (1.15 +- 0.81) and 9.9 +- 1.1 (2.1 +- 1.5) at near and far detectors, respectively, in a unit of 10^-8 μ^-1 g^-1 cm^2. Combining the measured ^9Li yields with other available underground measurements, an excellent power-law relationship of the yield with respect to the mean muon energy is found to have an exponent of α = 0.75 +- 0.05.

We present a nearly reactor model independent search for sterile neutrino oscillation using 2 509 days of RENO near detector data and 180 days of NEOS data. The reactor related systematic uncertainties are significantly suppressed as both detectors are located at the same reactor complex of Hanbit Nuclear Power Plant. The search is performed by electron antineutrino ((nu) over bar (e)) disappearance between six reactors and two detectors with flux-weighted baselines of 419 m (RENO) and 24 m (NEOS). A spectral comparison of the NEOS prompt-energy spectrum with a no-oscillation prediction from the RENO measurement can explore reactor (nu) over bar (e) oscillations to sterile neutrino. Based on the comparison, we obtain a 95% C.L. excluded region of 0.1 < vertical bar Delta m(4)(1)(2)vertical bar < 7 eV(2). We also obtain a 68% C.L. allowed region with the best fit of vertical bar Delta m(4)(1)(2)vertical bar = 2.41 eV(2) and sine(2) 2 theta(14) = 0.08 having a p-value of 8.2%. Comparisons of obtained reactor antineutrino spectra at reactor sources are made among RENO, NEOS, and Daya Bay to find a possible spectral variation.

(The RENO Collaboration) Department of Physics, Sungkyunkwan University, Suwon 16419, Korea Institute for High Energy Physics, Dongshin University, Naju 58245, Korea Department of Fire Safety, Seoyeong University, Gwangju 61268, Korea GIST College, Gwangju Institute of Science and Technology, Gwangju 61005, Korea Institute for Universe and Elementary Particles, Chonnam National University, Gwangju 61186, Korea Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea Department of Physics, Kyungpook National University, Daegu 41566, Korea (Dated: April 21, 2022)

JSNS ^2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of ν̅_μ→ν̅_e appearance oscillations using muon decay-at-rest neutrinos. Before dedicated data taking in the first-half of 2021, we performed a commissioning run for 10 days in June 2020. Using the data obtained in this commissioning run, in this paper, we present an estimate of the correlated background which imitates the ν̅_e signal in a sterile neutrino search. In addition, in order to demonstrate future prospects of the JSNS ^2 experiment, possible pulse shape discrimination improvements towards reducing cosmic ray induced fast neutron background are described.

Hyper-Kamiokande (HK) is the next generation underground water Cherenkov detector that builds on the highly successful Super-Kamiokande (SK) experiment. The 260,000-ton detector has an 8.4 times larger fiducial volume than its predecessor. HK's low energy threshold combined with the very large fiducial volume make the detector unique; HK is expected to acquire an unprecedented exposure of 3.8 Mton-year over a period of 20 years starting in 2027. It has an extremely diverse science program including long-baseline neutrino oscillation measurements, nucleon decay searches, atmospheric neutrinos, neutrinos from the sun and supernova explosions, and neutrinos from other astrophysical origins. Like DUNE, the flagship project of the U.S. high-energy physics program, HK measures fundamental properties of neutrinos such as the search for leptonic CP violation and neutrino physics beyond the Standard Model.

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.

The RENO experiment reports measured flux and energy spectrum of reactor electron antineutrinos nu over bar e from the six reactors at Hanbit Nuclear Power Plant. The measurements use 966 094 116 111 nu over bar e candidate events with a background fraction of 2.39% (5.13%), acquired in the near (far) detector, from August 2011 to March 2020. The inverse beta decay (IBD) yield is measured as o5.852 1 0.094 thorn x 10-43 cm2/fission, corresponding to 0.941 10.015 of the prediction by the Huber and Mueller (HM) model. A reactor nu over bar e spectrum is obtained by unfolding a measured IBD prompt spectrum. The obtained neutrino spectrum shows a clear excess around 6 MeV relative to the HM prediction. The obtained reactor nu over bar e spectrum will be useful for understanding unknown neutrino properties and reactor models. The observed discrepancies suggest the next round of precision measurements and modification of the current reactor nu over bar e models.

The Sterile Neutrino Search at the J-PARC Spallation Neutron Source (JSNS$^2$) experiment aims 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 of the photomultiplier tubes, 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 2020 June. In this paper, we present a description of the assembly and installation of the SCMS and its performance.

Supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants---neutron stars and black holes---are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic supernova in unprecedented detail. In this thesis, I investigate how well such an observation would allow us to reconstruct the explosion mechanism. I develop a high-precision supernova event generator and use a detailed detector simulation and event reconstruction to explore Hyper-Kamiokande's response to five supernova models simulated by different groups around the world. I show that 300 neutrino events in Hyper-Kamiokande---corresponding to a supernova at a distance of at least 60 kpc---are sufficient to distinguish between these models with high accuracy. These findings indicate that, once the next galactic supernova happens, Hyper-Kamiokande will be able to determine details of the supernova explosion mechanism.

The Reactor Experiment for Neutrino Oscillation (RENO) experiment has been taking data using two identical liquid scintillator detectors since August 2011. The experiment has observed the disappearance of reactor neutrinos in their interactions with free protons, followed by neutron capture on hydrogen (n-H). Based on 1500 live days of data taken with 16.8 GWth reactors at the Hanbit Nuclear Power Plant in Korea, the near (far) detector observes 567690 (90747) electron antineutrino candidate events with the n-H data. This provides an independent measurement of neutrino mixing angle θ13 and a consistency check on the validity of the result obtained from the data with neutron capture on Gadolinium (n-Gd). Furthermore, it provides an important cross-check on the systematic uncertainties of the n-Gd measurement. Based on a rate-only analysis, we obtain sin2 2θ13 = 0.086 ± 0.008(stat.) ± 0.014(syst.). The combination of this result with that of n-Gd is also reported.

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.

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 $Δm^2$ 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 $Δm^2$ 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.

The JSNS2 (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 JSNS2 inner detector is filled with 17 tons of gadolinium-loaded liquid scintillator (LS) and both the intermediate γ-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 either donated by other experiments or purchased from Hamamatsu. Donated PMTs were purchased around 10 years ago, therefore JSNS2 did pre-calibration of the PMTs including the purchased PMTs. 123 PMTs demonstrated acceptable performance for the JSNS2 experiment, and 120 PMTs were installed in the detector.