First Measurement of Solar B-8 Neutrinos via Coherent Elastic Neutrino-Nucleus Scattering with XENONnT

• Fei Gao (Tsinghua University)

Room: 227 (2nd Fl.) Solar neutrinos can interact with liquid xenon (LXe) in dark matter detectors through coherent elastic neutrino-nucleus scattering (CEvNS), generating signals that closely mimic dark matter (DM) interactions. This phenomenon, often referred to as the 'neutrino fog,' presents a significant challenge to direct DM detection efforts. The XENONnT detector, known for its large exposure and low background, offers an exceptional opportunity to investigate this interaction. At the heart of XENONnT is a low-background, two-phase time projection chamber with a 5.9-tonne liquid xenon target. Utilizing data from XENONnT's first and second science runs, we searched for CEvNS signals of solar B-8 neutrinos, resulting in 37 observed events above 0.5 keV, with the 26.4 (+1.4/-1.3) background events expected, led to the rejection of the background-only hypothesis with a statistical significance of 2.73-sigma. This marks the first direct detection of nuclear recoils from solar neutrinos using a dark matter detector. In this seminar, we will present a detailed view of the search for solar B-8 CEvNS signals. This includes the implementation of novel low-threshold analysis techniques, suppression of dominant accidental coincidence backgrounds, and advanced modeling of multidimensional signal and background distributions in statistical inference, all of which significantly enhance sensitivity to solar B-8 neutrinos.