Neutrinos at IceCube from Heavy Decaying Dark Matter

TL;DR

This paper investigates the possibility that two PeV neutrino events detected by IceCube are signals of monochromatic neutrino lines from decaying dark matter, exploring viable decay operators and associated spectra.

Contribution

It identifies specific dark matter decay candidates and operators that could produce PeV neutrino lines, linking observed events to dark matter physics.

Findings

PeV neutrino line signals could originate from dark matter decays.

Decays of gravitinos, gauge bosons, or singlet fermions can produce observable neutrino spectra.

A continuum neutrino spectrum is expected alongside the monochromatic line.

Abstract

A monochromatic line in the cosmic neutrino spectrum would be a smoking gun signature of dark matter. It is intriguing that the IceCube experiment has recently reported two PeV neutrino events with energies that may be equal up to experimental uncertainties, and which have a probability of being a background fluctuation estimated to be less than a percent. Here we explore prospects for these events to be the first indication of a monochromatic line signal from dark matter. While measurable annihilation signatures would seem to be impossible at such energies, we discuss the dark matter quantum numbers, effective operators, and lifetimes which could lead to an appropriate signal from dark matter decays. We will show that the set of possible decay operators is rather constrained, and will focus on several viable candidates which could explain the IceCube events; R-parity violating gravitinos, hidden sector gauge bosons, and singlet fermions in an extra dimension. In essentially all cases we find that a PeV neutrino line signal from dark matter would be accompanied by a potentially observable continuum spectrum of neutrinos rising towards lower energies.