A Combined Astrophysical and Dark Matter Interpretation of the IceCube HESE and Throughgoing Muon Events

Abstract

We perform a combined likelihood analysis for the IceCube 6-year high-energy starting events (HESE) and 8-year throughgoing muon events above 10 TeV using a two-component neutrino flux model. The two-component flux can be motivated either from purely astrophysical sources or due to a beyond Standard Model contribution, such as decaying heavy dark matter. We find that the astrophysical plus dark matter interpretation is mildly preferred by the current data over the purely astrophysical explanation. As for the astrophysical neutrinos, we consider two different source flavor compositions corresponding to the standard pion decay and muon-damped pion decay sources. We find that the latter is slightly preferred over the former as the high-energy component, while the low-energy component does not show any such preference. We also take into account the multi-messenger gamma-ray constraints and find that our two-component fit is compatible with these constraints, whereas the single-component power-law bestfit to the HESE data is ruled out. The astrophysical plus dark matter interpretation of the two-component flux is found to be mildly preferred by the current data and the gamma-ray constraints over the purely astrophysical explanation.