American Astronomical Society Acta Medica Okayama 0004-637X 992 1 2025 Observing Supernova Neutrino Light Curves with Super-Kamiokande. VI. A Practical Data Analysis Technique Considering Realistic Experimental Backgrounds 27 EN Fumi Nakanishi Department of Physics, Okayama University Ken’ichiro Nakazato Faculty of Arts and Science, Kyushu University Masayuki Harada Kamioka Observatory, Institute for Cosmic Ray Research, The University of Tokyo Yusuke Koshio Department of Physics, Okayama University Ryuichiro Akaho Faculty of Science and Engineering, Waseda University Yosuke Ashida Department of Physics, Tohoku University Akira Harada National Institute of Technology, Ibaraki College Masamitsu Mori Division of Science, National Astronomical Observatory of Japan Kohsuke Sumiyoshi National Institute of Technology, Numazu College Yudai Suwa Department of Earth Science and Astronomy, The University of Tokyo Roger A. Wendell Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, The University of Tokyo Masamichi Zaizen Department of Earth Science and Astronomy, The University of Tokyo Neutrinos from supernovae, especially those emitted during the late phase of core collapse, are essential for understanding the final stages of massive star evolution. We have been dedicated to developing methods for the analysis of neutrinos emitted during the late phase and observed at Super-Kamiokande (SK). Our previous studies have successfully demonstrated the potential of various analysis methods in extracting essential physical properties; however, the lack of background consideration has limited their practical application. In this study, we address this issue by incorporating a realistic treatment of the experimental signal and background events with the on-going SK experiment. We therefore optimize our analysis framework to reflect realistic observational conditions, including both signal and background events. Using this framework we study several long-time supernova models, simulating the late phase neutrino observation in SK and focusing in particular on the identification of the last observed event. We discuss the possibility of model discrimination methods using timing information from this last observed event. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 2050-3911 2025 1 2024 Modification on Thermal Motion in Geant4 for Neutron Capture Simulation in Gadolinium Loaded Water 013C01 EN Y. Hino Department of Physics, Okayama University K. Abe Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo R. Asaka Department of Physics, Faculty of Science and Technology, Tokyo University of Science S. Han Research Center for Cosmic Neutrinos, Institute for Cosmic Ray Research, University of Tokyo M. Harada Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo M. Ishitsuka Department of Physics, Faculty of Science and Technology, Tokyo University of Science H. Ito Department of Physics, Faculty of Science and Technology, Tokyo University of Science S. Izumiyama Department of Physics, Tokyo Institute of Technology Y. Kanemura Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo Y. Koshio Department of Physics, Okayama University F. Nakanishi Department of Physics, Okayama University H. Sekiya Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo T. Yano Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo Neutron tagging is a fundamental technique for electron anti-neutrino detection via the inverse beta decay channel. A reported discrepancy in neutron detection efficiency between observational data and simulation predictions prompted an investigation into neutron capture modeling in Geant4. The study revealed that an overestimation of the thermal motion of hydrogen atoms in Geant4 impacts the fraction of captured nuclei. By manually modifying the Geant4 implementation, the simulation results align with calculations based on evaluated nuclear data and show good agreement with observables derived from the SK-Gd data. No potential conflict of interest relevant to this article was reported.

IOP Publishing Ltd Acta Medica Okayama 0004-637X 965 1 2024 Supernova Burst and Diffuse Supernova Neutrino Background Simulator for Water Cherenkov Detectors 91 EN Fumi Nakanishi Department of Physics, Okayama University Shota Izumiyama Department of Physics, Tokyo Institute of Technology Masayuki Harada Department of Physics, Okayama University Yusuke Koshio Department of Physics, Okayama University If a Galactic core-collapse supernova explosion occurs in the future, it will be critical to rapidly alert the community to the direction of the supernova by utilizing neutrino signals in order to enable the initiation of follow-up optical observations. In addition, there is anticipation that observation of the diffuse supernova neutrino background will yield discoveries in the near future, given that experimental upper limits are approaching theoretical predictions. We have developed a new supernova event simulator for water Cherenkov neutrino detectors, such as the highly sensitive Super-Kamiokande. This simulator calculates the neutrino interaction in water for two simulation purposes, individual core-collapse supernova bursts and diffuse supernova neutrino background. Based on this simulator, we can evaluate the precision in determining the location of supernovae and estimate the expected number of events related to the diffuse supernova neutrino background in Super-Kamiokande. In this paper, we describe the basic structure of the simulator and its demonstration. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 2050-3911 2023 6 2023 Angular correlation of the two gamma rays produced in the thermal neutron capture on gadolinium-155 and gadolinium-157 063H01 EN Pierre Goux Department of Physics, Okayama University Franz Glessgen Department of Physics, Okayama University Enrico Gazzola Department of Physics, Okayama University Mandeep Singh Reen Department of Physics, Okayama University William Focillon Département de Physique, École Polytechnique, IN2P3/CNRS Michel Gonin Département de Physique, École Polytechnique, IN2P3/CNRS Tomoyuki Tanaka Department of Physics, Okayama University Kaito Hagiwara Department of Physics, Okayama University Ajmi Ali Department of Physics, Okayama University Takashi Sudo Department of Physics, Okayama University Yusuke Koshio Department of Physics, Okayama University Makoto Sakuda Department of Physics, Okayama University Gianmaria Collazuol INFN Sezione di Padova and Università di Padova, Dipartimento di Fisica Atsushi Kimura Japan Atomic Energy Agency Shoji Nakamura Japan Atomic Energy Agency Nobuyuki Iwamoto Japan Atomic Energy Agency Hideo Harada Japan Atomic Energy Agency Michael Wurm Institut für Physik, Johannes Gutenberg-Universität Mainz The ANNRI-Gd collaboration studied in detail the single gamma-ray spectrum produced from the thermal neutron capture on Gd-155 and Gd-157 in our previous publications. Gadolinium targets were exposed to a neutron beam provided by the Japan Spallation Neutron Source (JSNS) in J-PARC, Japan. In the present analysis, one new additional coaxial germanium crystal was used in combination with the 14 germanium crystals in the cluster detectors to study the angular correlation of the two gamma rays emitted in the same neutron capture. We present for the first time angular correlation functions for two gamma rays produced during the electromagnetic cascade transitions in the (n, gamma) reactions on Gd-155 and Gd-157. As expected, we observe mild angular correlations for the strong, but rare transitions from the resonance state to the two energy levels of known spin-parities. Contrariwise, we observe negligibly small angular correlations for arbitrary pairs of two gamma rays produced in the majority of cascade transitions from the resonance state to the dense continuum states. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 2050-3911 2020 4 2020 Gamma-ray spectra from thermal neutron capture on gadolinium-155 and natural gadolinium 043D02 EN Tomoyuki Tanaka Department of Physics, Okayama University Kaito Hagiwara Department of Physics, Okayama University Enrico Gazzola Universitá di Padova and INFN, Dipartimento di Fisica Ajmi Ali Department of Physics, Okayama University Iwa Ou Department of Physics, Okayama University Takashi Sudo Department of Physics, Okayama University Pretam Kumar Das Department of Physics, Okayama University Mandeep Singh Reen Department of Physics, Okayama University Rohit Dhir Department of Physics, Okayama University Yusuke Koshio Department of Physics, Okayama University Makoto Sakuda Department of Physics, Okayama University Atsushi Kimura Japan Atomic Energy Agency Shoji Nakamura Japan Atomic Energy Agency Nobuyuki Iwamoto Japan Atomic Energy Agency Hideo Harada Japan Atomic Energy Agency Gianmaria Collazuol Universitá di Padova and INFN, Dipartimento di Fisica Sebastian Lorenz Institut für Physik, Johannes Gutenberg-Universität Mainz Michael Wurm Institut für Physik, Johannes Gutenberg-Universität Mainz William Focillon Département de Physique, École Polytechnique Michel Gonin Département de Physique, École Polytechnique Takatomi Yano Kamioka Observatory, ICRR, University of Tokyo Natural gadolinium is widely used for its excellent thermal neutron capture cross section, because of its two major isotopes: Gd-155 and Gd-157. We measured the gamma-ray spectra produced from the thermal neutron capture on targets comprising a natural gadolinium film and enriched Gd-155 (in Gd2O3 powder) in the energy range from 0.11 MeV to 8.0 MeV, using the ANNRI germanium spectrometer at MLF, J-PARC. The freshly analyzed data of the Gd-155(n,gamma) reaction are used to improve our previously developed model (ANNRI-Gd model) for the Gd-157(n,gamma) reaction [K. Hagiwara et al. [ANNRI-Gd Collaboration], Prog. Theor. Exp. Phys. 2019, 023D01 (2019)], and its performance confirmed with the independent data from the Gd-nat(n,gamma) reaction. This article completes the development of an efficient Monte Carlo model required to simulate and analyze particle interactions involving the thermal neutron captures on gadolinium in any relevant future experiments. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2218-1997 6 6 2020 Observation of Atmospheric Neutrinos 80 EN Yusuke Koshio Experimental Particle Physics Group, Department of Physics, Okayama University In 1998, the Super-Kamiokande discovered neutrino oscillation using atmospheric neutrino anomalies. It was the first direct evidence of neutrino mass and the first phenomenon to be discovered beyond the standard model of particle physics. Recently, more precise measurements of neutrino oscillation parameters using atmospheric neutrinos have been achieved by several detectors, such as Super-Kamiokande, IceCube, and ANTARES. In addition, precise predictions and measurements of atmospheric neutrino flux have been performed. This paper presents the history, current status, and future prospects of the atmospheric neutrino observation. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 2050-3911 2 2019 Gamma-ray spectrum from thermal neutron capture on gadolinium-157 023D01 EN Kaito Hagiwara Department of Physics, Okayama University Takatomi Yano Institute for Cosmic Ray Research, University of Tokyo Tomoyuki Tanaka Department of Physics, Okayama University Mandeep Singh Reen Department of Physics, Okayama University Pretam Kumar Das Department of Physics, Okayama University Sebastian Lorenz Department of Physics, Okayama University Iwa Ou Department of Physics, Okayama University Takashi Sudo Department of Physics, Okayama University Yoshiyuki Yamada Department of Physics, Okayama University Takaaki Mori Department of Physics, Okayama University Tsubasa Kayano Department of Physics, Okayama University Rohit Dhir Department of Physics, Okayama University Yusuke Koshio Department of Physics, Okayama University Makoto Sakuda Department of Physics, Okayama University Atsushi Kimura Japan Atomic Energy Agency Shoji Nakamura Japan Atomic Energy Agency Nobuyuki Iwamoto Japan Atomic Energy Agency Hideo Harada Japan Atomic Energy Agency Michael Wurm Institut für Physik, Johannes Gutenberg-Universität Mainz William Focillon Département de Physique, École Polytechnique Michel Gonin Département de Physique, École Polytechnique Ajmi Ali Department of Physics, Okayama University Gianmaria Collazuol Universitá di Padova and INFN, Dipartimento di Fisica We have measured the -ray energy spectrum from the thermal neutron capture, Gd, on an enriched Gd target (GdO) in the energy range from 0.11 MeV up to about 8 MeV. The target was placed inside the germanium spectrometer of the ANNRI detector at J-PARC and exposed to a neutron beam from the Japan Spallation Neutron Source (JSNS). Radioactive sources (Co, Cs, and Eu) and the Cl(,) reaction were used to determine the spectrometers detection efficiency for rays at energies from 0.3 to 8.5 MeV. Using a Geant4-based Monte Carlo simulation of the detector and based on our data, we have developed a model to describe the -ray spectrum from the thermal Gd(,) reaction. While we include the strength information of 15 prominent peaks above 5 MeV and associated peaks below 1.6 MeV from our data directly into the model, we rely on the theoretical inputs of nuclear level density and the photon strength function of Gd to describe the continuum -ray spectrum from the Gd(,) reaction. Our model combines these two components. The results of the comparison between the observed -ray spectra from the reaction and the model are reported in detail. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 2050-3911 6 2019 Development of a method for measuring rare earth elements in the environment for future experiments with gadolinium-loaded detectors 063H03 EN S. Ito Okayama University, Faculty of Science T. Okada Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo Y. Takaku Institute for Environmental Sciences, Department of Radioecology M. Harada Okayama University, Faculty of Science M. Ikeda Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo Y. Kishimoto Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo Y. Koshio Okayama University, Faculty of Science M. Nakahata Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo Y. Nakajima Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo H. Sekiya Demand to use gadolinium (Gd) in detectors is increasing in the field of elementary particle physics, especially in neutrino measurements and dark matter searches. Large amounts of Gd are used in these experiments. To assess the impact of Gd on the environment it is becoming important to measure the baseline concentrations of Gd. Such measurement, however, is not easy due to interference by other elements. In this paper a method for measuring the concentrations of rare earth elements, including Gd, is proposed. In the method, inductively coupled plasma-mass spectrometry is utilized after collecting the dissolved elements in chelating resin. Results of the ability to detect anomalous concentrations of rare earth elements in river water samples in the Kamioka and Toyama areas are also reported. No potential conflict of interest relevant to this article was reported.