Dark matter annihilation in the Milky Way halo

Abstract

To constrain the particle properties of dark matter using their annihilation products, robust predictions of the annihilation rates are critical. Since the annihilation rate scales as the dark matter density squared, a precise knowledge of the distribution of dark matter is required. Given the popular galactic center contains large uncertainties in the dark matter density, we focus on the signal arising from the whole Milky Way halo. This is less sensitive to uncertainties in the dark matter distribution, and in terms of flux it is larger than the cosmic signal for halos flatter than NFW. We apply this to a dark matter model in which the principal annihilation products are neutrinos. Being the least detectable Standard Model particle, the neutrino defines a strong and general upper bound on the total annihilation cross section. We show that using the Milky Way halo signal improves previous limits by 1-2 orders of magnitude.(This article is based on H. Yuksel, S. Horiuchi, J. F. Beacom, S. Ando, ‘Neutrino Constraints on the Dark Matter Total Annihilation Cross Section,’ (2007 Phys. Rev. D 76 123506, arXiv:0707.0196).)