Bounds on Cross-sections and Lifetimes for Dark Matter Annihilation and Decay into Charged Leptons from Gamma-ray Observations of Dwarf Galaxies

Understand

We provide conservative bounds on the dark matter cross-section and lifetime from final state radiation produced by annihilation or decay into charged leptons, either directly or via an intermediate particle $\phi$.

• Our analysis utilizes the experimental gamma-ray flux upper limits from four Milky Way dwarf satellites: HESS observations of Sagittarius and VERITAS observations of Draco, Ursa Minor, and Willman 1.
• Using 90% confidence level lower limits on the integrals over the dark matter distributions, we find that these constraints are largely unable to rule out dark matter annihilations or decays as an explanation of the PAMELA and ATIC/PPB-BETS excesses.
• However, if there is an additional Sommerfeld enhancement in dwarfs, which have a velocity dispersion ~10 to 20 times lower than that of the local Galactic halo, then the cross-sections for dark matter annihilating through $\phi$'s required to explain the excesses are very close to the cross-section upper bounds from Willman 1.