Signals of a new gauge boson from IceCube and the muon g-2

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 diplike feature at E & nu; & SIM; 0.2-1 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 mZ' & SIM; 10 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 in better accordance with IceCube's measurement, in particular if the neutrinos observed by IceCube predominantly originate from high-redshift sources. We comment on some theoretical ingredients whose knowledge will be sharpened in the coming years and that should contribute to a more robust characterization and possible detection of the feature.