Distinguishing dark matter annihilation enhancement scenarios via halo shapes

Sommerfeld enhancement and Breit-Wigner enhancement of the dark matter annihilation have been proposed to explain the “boost factor” which is suggested by observed cosmic ray excesses. Although these two scenarios can provide almost indistinguishable effects on the cosmic ray fluxes, the cross sections of the self-interaction in those enhancement mechanisms are drastically different. As a result, we might be able to distinguish them by examining the effects of the self-interaction on the dark matter halo shapes. In the Sommerfeld enhancement models with mϕ≲100 MeV and mDM≲3 TeV, the self-interaction of dark matter can lead to more spherical dark halo. In the Breit-Wigner models, the dark matter is effectively collisionless.