Search for Diffuse Supernova Neutrino Background with 956.2 Days of Super-Kamiokande Gadolinium Dataset
Abstract We report the search result for the Diffuse Supernova Neutrino Background (DSNB) in neutrino energies beyond 9.3 MeV in the gadolinium-loaded Super-Kamiokande (SK) detector with a 22,500 × 956.2 m 3 day exposure. Starting in the summer of 2020, SK introduced 0.01% gadolinium (Gd) by mass into its ultrapure water to enhance the neutron capture signal, termed the SK-VI phase. This was followed by a 0.03% Gd-loading in 2022, a phase referred to as SK-VII. We then conducted a DSNB search using 552.2 days of SK-VI data and 404.0 days of SK-VII data through 2023 September. This analysis includes several new features, such as two new machine learning neutron detection algorithms with Gd, an improved atmospheric background-reduction technique, and two parallel statistical approaches. No significant excess over background predictions was found in a DSNB spectrum-independent analysis, and 90% confidence level (C.L.) upper limits on the astrophysical electron antineutrino flux were set. Additionally, a spectral fitting result exhibited a ∼1.2 σ disagreement with a null DSNB hypothesis, comparable to a previous result from 5823 days of all SK pure-water phases.
Authors
- T. Kajita (ORCID: https://orcid.org/0000-0003-1207-6638)
- Takuji Nakamura (ORCID: https://orcid.org/0000-0002-3876-2946)
- L. Ludovici (ORCID: https://orcid.org/0000-0003-1970-9960)
- K. Choi (ORCID: https://orcid.org/0000-0002-0932-9123)
- R Shinoda
- Lorenzo Périssé (ORCID: https://orcid.org/0000-0003-3444-4454)
- Y. Hayato (ORCID: https://orcid.org/0000-0002-8683-5038)
- M. Feltre (ORCID: https://orcid.org/0000-0002-0489-3913)
- Y. Kanemura
- S. Miki
- R. Rogly (ORCID: https://orcid.org/0000-0003-2530-5217)
- J.S Jang
- K Hosokawa
- N.J Griskevich
- H. Sekiya
- R. P. Litchfield (ORCID: https://orcid.org/0000-0002-5914-4733)
- Keisuke Okumura (ORCID: https://orcid.org/0000-0002-9491-7367)
- Y. Kataoka
- R.G Park
- B. Zaldivar
- B. S. Yang (ORCID: https://orcid.org/0000-0001-5877-6096)
- M. Nakahata (ORCID: https://orcid.org/0000-0001-7783-9080)
- G. De Rosa (ORCID: https://orcid.org/0000-0002-2197-511X)
- L. Wan (ORCID: https://orcid.org/0000-0001-5524-6137)
- Y Asaoka
- Pascal Paganini (ORCID: https://orcid.org/0000-0001-9580-683X)
- Tzu-Chiao Hung (ORCID: https://orcid.org/0000-0002-2036-2338)
- Ryo Nishijima
- L. N. Machado (ORCID: https://orcid.org/0000-0002-7578-4183)
- T. Yano (ORCID: https://orcid.org/0000-0002-5320-1709)
- X. Wang
- V. Berardi (ORCID: https://orcid.org/0000-0002-8387-4568)
- Caroline Quach (ORCID: https://orcid.org/0000-0002-1170-9475)
- J. Kameda (ORCID: https://orcid.org/0000-0002-2963-2402)
- Yuji Noguchi (ORCID: https://orcid.org/0000-0001-7720-1837)
- Y. Uchida
- Y. Satou (ORCID: https://orcid.org/0000-0003-3627-0435)
- E. Radicioni
- S. H. Lee (ORCID: https://orcid.org/0000-0003-3523-9479)
- T. Wester (ORCID: https://orcid.org/0000-0001-6668-7595)
- K Hiraide
- D. H. Moon (ORCID: https://orcid.org/0000-0002-5628-9187)
- A. Langella (ORCID: https://orcid.org/0000-0001-6273-3558)
- Y. Suzuki (ORCID: https://orcid.org/0000-0001-7340-6675)
- A. D. Santos (ORCID: https://orcid.org/0009-0006-6769-3544)
- G. Collazuol (ORCID: https://orcid.org/0000-0002-7876-6124)
- B. W. Pointon (ORCID: https://orcid.org/0000-0003-0312-4044)
- N. Ospina (ORCID: https://orcid.org/0000-0002-8404-1808)
- Yasuhiko Takemoto (ORCID: https://orcid.org/0000-0002-3051-1667)
- M. Shiozawa (ORCID: https://orcid.org/0000-0003-0520-3520)
- M. Ikeda
- J. Hill
- H. W. Sobel
- P. Fernández (ORCID: https://orcid.org/0000-0001-9034-1930)
- T Tashiro
- M G Catanesi
- M. Miura
- C. Yanagisawa (ORCID: https://orcid.org/0000-0002-6490-1743)
- O. Drapier
- L. Labarga (ORCID: https://orcid.org/0000-0002-6395-9142)
- J. Bian
- B Quilain
- H. Tanaka
- M. Gonin
- S Moriyama
- K. Scholberg
- A Beauchene
- M. Smy
- N.F Calabria
- K. Ieki
- S. Nakayama
- K. Abe
- J. G. Learned
- Tomoaki Tomiya
- Marie-Pierre Férey
- Y. Jiang (ORCID: https://orcid.org/0000-0002-8964-5109)
- A. Takeda (ORCID: https://orcid.org/0009-0003-6003-072X)
- M. C. Jang
- D Samudio
- E Le Blévec
Institutions
- California State University System (US)
- State University of New York (US)
- University of Hawaii System (US)
- University of Padua (IT)
- High Energy Accelerator Research Organization (JP)
- Borough of Manhattan Community College (US)
- Duke University (US)
- British Columbia Institute of Technology (CA)
- University of California System (US)
- Gwangju Institute of Science and Technology (KR)
- Chonnam National University Hospital (KR)
- Institute for Basic Science (KR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Padova (IT)
- Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (IT)
- Istituto Nazionale di Fisica Nucleare, Sezione di Bari (IT)
- Laboratoire Leprince-Ringuet (FR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma I (IT)
- Gifu University (JP)
- Imperial College London (GB)
- Stony Brook University (US)
- Nagoya University (JP)
- Universidad Autónoma de Madrid (ES)
- Polytechnic University of Bari (IT)
- The University of Tokyo (JP)
- University of Glasgow (GB)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2026-06-29
- DOI
- https://doi.org/10.3847/1538-4357/ae6c20
- Primary Topic
- Neutrino Physics Research
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- U.S. Department of Energy
- European Commission
- National Research Foundation
- Ministry of Education, Culture, Sports, Science and Technology
- National Natural Science Foundation of China
- National Research Foundation of Korea
- Institute for Basic Science
- Horizon 2020 Framework Programme
- Natural Sciences and Engineering Research Council of Canada
- Science and Technology Facilities Council
- Japan Society for the Promotion of Science
- Nuclear Physics