Weakly Interacting Massive Particle Distribution in and Evaporation from the Sun

The paper analyzes the evaporation of weakly interacting massive particles (WIMPs) from the sun, both analytically and numerically. First, an analytic approximation is made by defining an appropriate truncation of a Maxwell-Boltzmann distribution for the WIMPs and calculating the exact evaporation rate from this distribution due to interaction with a truly thermal distribution of nuclei. Then, the actual (nonthermal) distribution of Dirac neutrino WIMPs in the sun is calculated numerically for WIMPs of mass 1-7 GeV. Evaporation from the actual and thermal distributions is compared. It is found that the evaporation mass for a solar lifetime is 3.7 GeV, and for an 'annihilation lifetime', 2.9 GeV. These are about 8 percent lower than the most well-reasoned previous estimate.