Speaker
Description
Speaker: Bhupal Dev
Abstract: The lowest-energy neutrinos detected to date are those produced in the solar proton–proton (pp) chain, with energies above approximately 200 keV. The Sun is also expected to emit an even lower-energy flux of thermal neutrinos at the keV scale, generated through standard electroweak processes in the solar plasma. Despite their fundamental connection to solar physics, these thermal neutrinos have so far remained undetected. We show that thermal solar neutrinos are kinematically accessible to large-volume dark matter direct-detection experiments through electron-ionization signals. Using recent data from the XENONnT experiment, we derive the first upper limit on the thermal solar neutrino flux, constraining it to be below 10^8 times the Standard Model prediction. Future experiments such as XLZD could improve this sensitivity by several orders of magnitude. Although a detection remains out of reach with the current technology, our results establish future low-threshold direct-detection experiments as a promising avenue for probing the lowest-energy neutrino sources in astrophysics. This opens a new observational window on stellar interiors and could also provide a novel test of beyond-the-Standard-Model physics at the low-energy neutrino frontier.