Neutrino self-interactions and XENON1T electron recoil excess

Abstract

The XENON1T collaboration recently reported an excess in electron recoil events in the energy range between $1-7\,\mathrm{keV}$. This excess could be understood to originate from the known solar neutrino flux, if neutrinos couple to a light vector-mediator with strength $g_{\nu N}$ that kinetically mixes with the photon with strength $\chi$, and $g_{\nu N}\chi\sim10^{-13}$. Here, we show that such coupling values can naturally arise in a renormalizable model of long-range vector-mediated neutrino self-interactions. The model could be discriminated from other explanations of the XENON1T excess by the characteristic $1/T^2$ energy dependence of the neutrino-electron scattering cross section. Other signatures include invisible Higgs and $Z$ decays and lepto-philic charged Higgses at a few $100\,\mathrm{GeV}$. ALPS II will probe part of the viable parameter space.