Can nonstandard neutrino interactions explain the XENON1T spectral excess?

Abstract

We perform a constrained spectral fit analysis of the excess observed in the electron recoil energy spectrum by XENON1T with neutrino magnetic moment, charge radius, neutrino millicharge and new light vector and scalar mediators. Within limits allowed by other laboratory experiments we find that the excess can be explained in the range (2−4)×10−11μB for the magnetic moment, (2−6)×10−31 cm2 for the charge radius, (1.7−2.3)×10−12e for the millicharge and (10−100) keV masses of light mediators with couplings of 3.5×10−7 for vector/axial-vector, 1×10−6 and 4×10−6 for scalar and pseudo-scalar mediators respectively. Among all neutrino millicharge, magnetic moment and vector mediators fit better to the observed spectrum. We also derive constraints on all new physics parameters considered here.