Analysis of heavy neutrinos as a dark matter candidate (original) (raw)

Context. Neutrinos heavier than MZ/2 ∼ 45 GeV are not excluded by particle physics data. Stable neutrinos heavier than this might contribute to the dark matter content of the universe as well as to the cosmic gamma ray background through annihilation in galaxies. Aims. We calculate the evolution of the heavy neutrino density in the universe as a function of their mass, MN and then the subsequent gamma ray spectrum from annihilation of distant NN̄ (from 0 < z < 5). This includes estimating the enhancement of the signal due to dark matter clumping. Methods. The evolution of the heavy neutrino density in the universe is calculated numerically. In order to obtain the enhancement due to the increased density within galaxies, we approximate the distribution of N to be proportional to that of dark matter in the GalICS model. The calculated gamma ray spectrum is compared to the measured EGRET data. Results. Heavy neutrinos of mass 120 . MN . 155 GeV could account for the entire dark m...