Gamma-ray Constraints on Hadronic and Leptonic Activities of Decaying Dark Matter

TL;DR

This paper derives gamma-ray constraints on dark matter decay modes, showing it must decay mainly into muons or taus to explain cosmic-ray excesses without conflicting with gamma-ray observations.

Contribution

It provides the first comprehensive gamma-ray constraints on both hadronic and leptonic dark matter decay channels using Fermi and HESS data.

Findings

Dark matter decay into mu+mu- or tau+tau- is favored.

Hadronic decay modes are strongly constrained by gamma-ray data.

Decaying dark matter can explain cosmic-ray excesses within these constraints.

Abstract

While the excess in cosmic-ray electrons and positrons reported by PAMELA and Fermi may be explained by dark matter decaying primarily into charged leptons, this does not necessarily mean that dark matter should not have any hadronic decay modes. In order to quantify the allowed hadronic activities, we derive constraints on the decay rates of dark matter into WW, ZZ, hh, qqbar and gg using the Fermi and HESS gamma-ray data. We also derive gamma-ray constraints on the leptonic e+e-, mu+mu- and tau+tau- final states. We find that dark matter must decay primarily into mu+mu- or tau+tau- in order to simultaneously explain the reported excess and meet all gamma-ray constraints.