Anomalies in direct and indirect detection have motivated models of dark matter consisting of a multiplet of nearly-degenerate states , coupled by a new GeV-scale interaction .
We perform a careful analysis of the thermal freezeout of dark matter annihilation in such a scenario .
We compute the range of “ boost factors ” arising from Sommerfeld enhancement in the local halo for models which produce the correct relic density , and show the effect of including constraints on the saturated enhancement from the cosmic microwave background ( CMB ) .
We find that boost factors from Sommerfeld enhancement of up to \sim 800 are possible in the local halo .
When the CMB bounds on the saturated enhancement are applied , the maximal boost factor is reduced to \sim 400 for 1-2 TeV dark matter and sub-GeV force carriers , but remains large enough to explain the observed Fermi and PAMELA electronic signals .
We describe regions in the DM mass-boost factor plane where the cosmic ray data is well fit for a range of final states , and show that Sommerfeld enhancement alone is enough to provide the large annihilation cross sections required to fit the data , although for light mediator masses ( m _ { \phi } \lesssim 200 MeV ) there is tension with the CMB constraints in the absence of astrophysical boost factors from substructure .
Additionally , we consider the circumstances under which WIMPonium formation is relevant and find for heavy WIMPs ( \stackrel { > } { \sim } 2 { ~ { } TeV } ) and soft-spectrum annihilation channels it can be an important consideration ; we find regions with m _ { \chi } \gtrsim 2.8 { ~ { } TeV } that are consistent with the CMB bounds with \mathcal { O } ( 600-700 ) present-day boost factors .