Speaker
Description
The XENONnT collaboration recently announced the detection of the lowest-energy $pp$ solar neutrinos to date, observed through scattering with atomically bound electrons. We discuss the important implications of this result for neutrino physics and for physics beyond the Standard Model. We place the measurement in the landscape of theoretical predictions and past experimental results. We show how the measurement, and the resulting tension with Standard Model expectations, depend strongly on the atomic response model used to describe elastic neutrino-electron scattering, and the level of $^{14}\text{C}$ contamination. Finally, in the context of physics beyond the Standard Model, we show that, in combination with Borexino’s results, XENONnT’s low-energy $pp$ neutrino measurement places leading constraints on quasi-Dirac neutrinos and neutrino lifetimes.