Kavli Affiliate: Masayuki Nakahata
| First 5 Authors: K. Abe, K. Abe, , ,

| Summary:
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 $22,500times956.2$$~rm m^3cdot day$ exposure. %$22.5rm ktimes956.2$$~rm m^3cdot day$ exposure. Starting in the summer of 2020, SK introduced 0.01% gadolinium (Gd) by mass into its ultra-pure 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 September 2023. 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% C.L. upper limits on the astrophysical electron anti-neutrino flux were set. Additionally, a spectral fitting result exhibited a $sim1.2σ$ disagreement with a null DSNB hypothesis, comparable to a previous result from 5823~days of all SK pure water phases.
| Search Query: arXiv Query: search_query=au:”Nakahata Masayuki”&id_list=&start=0&max_results=3
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