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First results from the search for an excess of ${\bar{ν}}_{e}$ events in ${JSNS}^{2}$

D. H. Lee ^1,†, S. Ajimura², A. Antonakis³, M. Botran³, M. K. Cheoun⁴, J. H. Choi⁵, J. W. Choi⁶, J. Y. Choi⁷, T. Dodo^8,9 et al. (JSNS Collaboration)

T. Dodo^8,9, H. Furuta⁸, J. H. Goh¹⁰, M. Harada¹¹, S. Hasegawa^9,11, Y. Hino^8,‡, T. Hiraiwa^2,§, W. S. Hwang¹⁰, T. Iida¹², E. Iwai^3,§, S. Iwata^13,∥, H. I. Jang⁷, J. S. Jang¹⁴, M. C. Jang⁶, H. K. Jeon¹⁵, S. H. Jeon⁵, K. K. Joo⁶, D. E. Jung⁶, S. K. Kang¹⁶, Y. Kasugai¹¹, T. Kawasaki¹³, E. M. Kim⁶, E. J. Kim¹⁷, J. Y. Kim⁶, S. Y. Kim⁶, S. B. Kim¹⁸, W. Kim¹⁹, H. Kinoshita¹¹, T. Konno¹³, K. Kuwata⁸, S. Lee¹⁰, I. T. Lim⁶, C. Little³, T. Maruyama¹, E. Marzec³, S. Masuda¹¹, S. Meigo¹¹, S. Monjushiro¹, D. H. Moon⁶, T. Nakano², M. Niiyama²⁰, K. Nishikawa^1,*, M. Noumachi², M. Y. Pac⁵, B. J. Park¹⁹, H. W. Park⁶, J. B. Park⁴, Jisu Park⁶, J. S. Park¹⁹, R. G. Park⁶, S. J. M. Peeters²¹, G. Roellinghoff¹⁵, C. Rott²², J. W. Ryu¹⁹, K. Sakai¹¹, S. Sakamoto¹¹, T. Shima², C. D. Shin⁵, J. Spitz³, I. Stancu²³, F. Suekane⁸, Y. Sugaya², K. Suzuya¹¹, M. Taira¹, Y. Takeuchi¹², W. Wang¹⁸, J. Waterfield²¹, W. Wei¹⁸, R. White²¹, Y. Yamaguchi¹¹, M. Yeh²⁴, I. S. Yeo⁵, C. Yoo¹⁰, I. Yu¹⁵, and A. Zohaib⁶ (JSNS Collaboration)

¹High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
²Research Center for Nuclear Physics, Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan
³University of Michigan, 500 S. State Street, Ann Arbor, Michigan 48109, USA
⁴Department of Physics and OMEG Institute, Soongsil University, 369 Sangdo-ro, Dongjak-gu, Seoul, 06978, Korea
⁵Laboratory for High Energy Physics, Dongshin University, 67, Dongshindae-gil, Naju-si, Jeollanam-do, 58245, Korea
⁶Department of Physics, Chonnam National University, 77, Yongbong-ro, Buk-gu, Gwangju, 61186, Korea
⁷Department of Fire Safety, Seoyeong University, 1 Seogang-ro, Buk-gu, Gwangju, 61268, Korea
⁸Research Center for Neutrino Science, Tohoku University, 6-3 Azaaoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan
⁹Advanced Science Research Center, JAEA, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
¹⁰Department of Physics, Kyung Hee University, 26, Kyungheedae-ro, Dongdaemun-gu, Seoul 02447, Korea
¹¹J-PARC Center, JAEA, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
¹²Faculty of Pure and Applied Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8571, Japan
¹³Department of Physics, Kitasato University, 1 Chome-15-1 Kitazato, Minami Ward, Sagamihara, Kanagawa, 252-0329, Japan
¹⁴GIST College, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, 61005, Korea
¹⁵Department of Physics, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do, 16419, Korea
¹⁶School of Liberal Arts, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul, 139-743, Korea
¹⁷Division of Science Education, Jeonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do, 54896, Korea
¹⁸School of Physics, Sun Yat-sen (Zhongshan) University, Haizhu District, Guangzhou, 510275, China
¹⁹Department of Physics, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu, 41566, Korea
²⁰Department of Physics, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto-City, 603-8555, Japan
²¹Department of Physics and Astronomy, University of Sussex, Falmer, Brighton, BN1 9RH, United Kingdom
²²Department of Physics and Astronomy, University of Utah, 201 Presidents’ Circle, Salt Lake City, Utah 84112, USA
²³University of Alabama, Tuscaloosa, Alabama, 35487, USA
²⁴Brookhaven National Laboratory, Upton, New York 11973-5000, USA

^*Deceased.
^†Contact author: leedh@post.kek.jp
^‡Now at KEK.
^§Now at RIKEN.
^∥Now at Tokyo Metropolitan College of Industrial Technology (Tokyo Metro. Col. of Indus. Tech.).

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Phys. Rev. D 113, 112011 – Published 24 June, 2026

DOI: https://doi.org/10.1103/272d-zws9

Abstract

The ${JSNS}^{2}$ (J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source) experiment at the Material and Life Science Facility (MLF) of J-PARC is designed to directly test an excess on ${\bar{ν}}_{e}$ events which was indicated by the Liquid Scintillator Neutrino Detector (LSND). The combination of a short-pulsed proton beam and a gadolinium-loaded liquid scintillator provides an excellent signal-to-noise ratio. In this article, we report the first results of a direct test based on data collected in 2022. After applying all event selection criteria, two events are observed, consistent with the expected background of $2.3 \pm 0.4$ events. No excess of ${\bar{ν}}_{e}$ events are seen in this report, however the expected number of events due to LSND anomaly is $1.1 \pm 0.5$ , thus this result is not yet conclusive. Data taking has been ongoing since 2021 and will continue in future runs. In addition, a new far detector has recently been constructed for the second phase experiment, ${JSNS}^{2}$ -II, marking an important milestone toward forthcoming measurements.

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References (23)

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Phys. Rev. D 113, 112011– Published 24 June, 2026

Vol. 113, Iss. 11 — 1 June 2026

Received 5 February 2026
Accepted 7 May 2026

DOI: https://doi.org/10.1103/272d-zws9

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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First results from the search for an excess of ${\bar{ν}}_{e}$ events in ${JSNS}^{2}$

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First results from the search for an excess of ${\bar{ν}}_{e}$ events in ${JSNS}^{2}$