The $L_\mu-L_\tau$ solution to the IceCube Ultra High Energy neutrino deficit in light of NA64

TL;DR

This paper proposes that a MeV-scale $L___ au$ gauge boson could explain the IceCube ultra-high-energy neutrino deficit and the muon g-2 anomaly, with future experiments poised to test this hypothesis.

Contribution

It introduces a model where a light $L___ au$ gauge boson explains neutrino spectrum anomalies and muon g-2, and maps the parameter space consistent with current and future experimental constraints.

Findings

The $L___ au$ gauge boson can account for IceCube neutrino spectrum features.

Certain parameter regions remain unexplored by current NA64$$ data.

Future NA64$$ runs can fully probe the relevant parameter space.

Abstract

In this work we analyze the scenario where a MeV scale $L_\mu - L_\tau$ gauge boson can explain the deficit in the diffuse ultra high energy (UHE) astrophysical neutrino spectrum observed in IceCube, as well as the discrepancy between experimental and $e^+e^-$ dispersion data driven SM 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$\mu$ results, we find that some part of the parameter space remains unexplored, but at a data volume of $10^{11}$ muons on target NA64$\mu$ will completely probe this region.