Sommerfeld Effect For Relic Density Of Asymmetric Dark Matter

In this paper,we discussed the relic density of asymmetric dark matter when the annihilation cross sections of asymmetric dark matter particles and antiparticles are changed by Sommerfeld enhancement.We specifically study the effect of Sommerfeld enhancement on the relic density of asymmetric dark matter particles and antiparticles when the mass of force carriers m_??0.We also discussed the effect of kinetic decoupling on the relic density of asymmetric dark matter particles and antiparticles when the annihilation cross section is boosted by Sommerfeld enhancement.We use the Mathematica to calculate the numerical results.The results show that the relic abundance of asymmetric dark matter decreases continuously until the Sommerfeld enhancement is saturated at low velocity.We also find that the decrease of antiparticle abundance is more significant than the particle abundance,and the level of decrease depends on the kinetic decoupling temperature and coupling strength?.For example,when the kinetic decoupling temperature is closer to the freeze out temperature,there will be a larger decrease.At the end,We used the observed data of dark matter,found the constraints on the annihilation cross section and asymmetry factor in the presence of Sommerfeld enhancement.We find that the annihilation cross section with Sommerfeld enhancement is smaller than without Sommerfeld enhancement.The annihilation cross section in the case of kinetic decoupling is smaller than without the kinetic decoupling.These results that imply the dark matter antiparticles may have significant indirect detection signals,it is important for dark matter detection experiments.It means that it is possible to explore asymmetric dark matter by observing the cosmic microwave background(CMB)?the Milky way and dwarf galaxies.