Searching for MeV-Scale Gauge Bosons with IceCube

TL;DR

This paper investigates how IceCube can detect MeV-scale gauge bosons through their effects on high-energy astrophysical neutrino spectra, identifying potential absorption features and current experimental constraints.

Contribution

It provides a detailed analysis of IceCube's sensitivity to light $Z'$ gauge bosons and proposes using neutrino flavor ratios to enhance detection prospects.

Findings

Light $Z'$ bosons cause observable absorption features in neutrino spectra.

Current IceCube data excludes $Z'$ lighter than a few MeV with couplings above $10^{-4}$.

Flavor ratio measurements can improve sensitivity to exotic physics.

Abstract

Light gauge bosons can lead to resonant interactions between high-energy astrophysical neutrinos and the cosmic neutrino background. We study this possibility in detail, considering the ability of IceCube to probe such scenarios. We find the most dramatic effects in models with a very light $Z'$ ($m_{Z'} \lesssim 10$ MeV), which can induce a significant absorption feature at $E_{\nu} \sim\,$5-10$\,{\rm TeV} \times (m_{Z'}/{\rm MeV})^2$. In the case of the inverted hierarchy and a small sum of neutrino masses, such a light $Z'$ can result in a broad and deep spectral feature at $\sim\,$0.1-10$\,{\rm PeV} \times (m_{Z'}/{\rm MeV})^2$. Current IceCube data already excludes this case for a $Z'$ lighter than a few MeV and couplings greater than $g\sim10^{-4}$. We emphasize that the ratio of neutrino flavors observed by IceCube can be used to further increase their sensitivity to $Z'$ models and to other exotic physics scenarios.