High-energy astrophysical neutrinos from cosmic strings

Abstract

Cosmic strings that couple to neutrinos may account for a portion of the high-energy astrophysical neutrino (HEAN) flux seen by IceCube. Here, we calculate the observed spectrum of neutrinos emitted from a population of cosmic-string loops that contain quasicusps, quasikinks, or kink-kink collisions. We consider two broad neutrino emission models: one where these string features emit a neutrino directly, and one where they emit a scalar particle which then eventually decays to a neutrino. In either case, we find the spectrum of cosmic-string neutrinos to follow a two-parameter model described by a power law with a high-energy cutoff. While none of the models in question fully match the observed HEAN spectrum, we do find that the maximum contribution of cosmic-string neutrinos can still be an $\mathcal{O}(1)$ fraction of the observed flux in addition to producing a bump in the observed neutrino spectrum. Finally, for each of the models presented, we present the viable parameter space for neutrino emission.