Lμ−Lτ solution to the IceCube ultrahigh-energy neutrino deficit in light of NA64

Abstract

In this work we analyze the scenario where a MeV scale Lμ−Lτ gauge boson can explain the deficit in the diffuse ultrahigh-energy (UHE) astrophysical neutrino spectrum observed in IceCube, as well as the discrepancy between experimental and e+e− scattering data-driven Standard Model calculations of the muon anomalous magnetic moment. We map the parameter space of the model where the elastic resonant s-channel scattering of UHE neutrinos with the cosmic neutrino background, mediated by the new Z′, can improve the description of the observed cascade and track spectra over the no-scattering hypothesis. Comparing to recent NA64-μ results, we find that some part of the parameter space remains unexplored, but at a data volume of 1011 muons on target NA64-μ will completely probe this region. Published by the American Physical Society 2024