Boosted Dark Matter and its implications for the features in IceCube HESE data (1612.02834v3)

Abstract: We study the implications of the premise that any new, relativistic, highly energetic neutral particle that interacts with quarks and gluons would create cascade-like events in the IceCube (IC) detector. Such events would be observationally indistinguishable from neutral current deep-inelastic scattering events due to neutrinos. Consequently, one reason for deviations, breaks or excesses in the expected astrophysical power-law neutrino spectrum could be the flux of such a particle. Motivated by features in the recent 1347-day IceCube high energy starting event data (HESE), we focus on particular boosted dark matter ($\chi$) related realizations of this premise. Here, $\chi$ is assumed to be much lighter than, and the result of, the slow decay of a massive scalar ($\phi$) which constitutes a major fraction of the Universe's dark matter. We show that this hypothesis, coupled with a standard power-law astrophysical neutrino flux is capable of providing very good fits to the present data, along with a possible explanation of other features in the HESE sample. These features include a) the paucity of events beyond $\sim 2$ PeV b) a spectral feature resembling a dip or a spectral change in the 400 TeV--1 PeV region and c) an excess in the $50-100$ TeV region. We consider two different boosted DM scenarios, and determine the allowed mass ranges and couplings for four different types of mediators (scalar, pseudoscalar, vector and axial-vector) which could connect the standard and dark sectors. We consider constraints from gamma-ray observations and collider searches. We find that the gamma-ray observations provide the most restrictive constraints, disfavouring the $1\sigma$ allowed parameter space from IC fits, while still being consistent with the $3\sigma$ allowed region. We also test our proposal and its implications against IC's recent six-year through-going muon track data.