Relic Density Of Asymmetric Dark Matter With Sommerfeld Enhancement

The Sommerfeld effect enhances the late-time Dark Matter annihilation signals,and the Sommerfeld enhancement is determined by the coupling of Dark Matter to the light force mediator.Asymmetric Dark Matter needs stronger couplings than symmetric Dark Matter of the same mass.Thus,the implications of the Sommerfeld enhancement for the phenomenology of asymmetric Dark Matter may be quite important compared with the symmetric Dark Matter case.We investigate the evolution of abundance of the asymmetric cold Dark Matter when its annihilation rate at chemical decoupling is boosted by the Sommerfeld enhancement.Next,we discuss the effect of kinetic decoupling on the relic abundance of asymmetric Dark Matter when the interaction rate depends on velocity.Usually,the relic density of asymmetric Dark Matter is analyzed in the frame of chemical decoupling.Indeed,after decoupling from chemical equilibrium,asymmetric Dark Matter particles and anti-particles are still in kinetic equilibrium for a while.This has no effect for the case of s-wave annihilation since there is no temperature dependence in this case.However,kinetic decoupling has impacts for the case of p-wave annihilation and Sommerfeld enhanced s-and p-wave annihilations.We investigate in detail the extent to which kinetic decoupling affects the relic abundance of asymmetric Dark Matter particles and anti-particles.Finally,we use the observational data of the relic density of Dark Matter to find the constraints on the cross section and asymmetry factor.The parameter space which is obtained provides us the possibility of probing asymmetric Dark Matter with observations of the Cosmic Microwave Background(CMB),the Milky way,and Dwarf galaxies.