Signals of a New Gauge Boson from IceCube and Muon $g-2$

TL;DR

This paper explores how a new $Z'$ gauge boson linked to a broken $U(1)_{L_{\mu}-L_{ au}}$ symmetry could explain the IceCube neutrino spectrum dip and the muon $g-2$ anomaly through resonant neutrino scattering.

Contribution

It demonstrates that a $Z'$ boson with parameters resolving the $g_ ext{ extmu}-2$ anomaly can also produce spectral features consistent with IceCube observations.

Findings

A $Z'$ with $m_{Z'} \, \sim \, 10$ MeV can cause resonant neutrino scattering.

The model can produce IceCube-like spectral dips for high-redshift sources.

The $Z'$ parameters simultaneously address the $g_ ext{ extmu}-2$ anomaly.

Abstract

A $Z'$ boson associated with a broken $U(1)_{L_{\mu} - L_{\tau}}$ gauge symmetry offers an economical solution to the long-standing $g_\mu-2$ anomaly, confirmed and strengthened by recent measurements at Fermilab. Here, we revisit the impact of such a $Z'$ on the spectrum of high-energy astrophysical neutrinos, as measured by the IceCube experiment. This spectrum has been observed to exhibit a dip-like feature at $E_{\nu} \sim 0.2-1 \, {\rm PeV}$, which could plausibly arise from the physics of the sources themselves, but could also be the consequence of high-energy neutrinos resonantly scattering with the cosmic neutrino background, mediated by a $Z'$ with a mass on the order of $m_{Z'} \sim 10 \, {\rm MeV}$. In this study, we calculate the impact of such a $Z'$ on the high-energy neutrino spectrum for a variety of model parameters and source distributions. For couplings that can resolve the $g_{\mu}-2$ anomaly, we find that this model could self-consistently produce a spectral feature that is consistent with IceCube's measurement, in particular if the neutrinos observed by IceCube predominantly originate from high-redshift sources.