Gamma ray lines from TeV dark matter

Abstract

We calculate, using unitarity, a lower bound on the branching ratio $\chi \chi \to \gamma \gamma$ and $\chi \chi \to \gamma Z$, where $\chi$ is any halo dark matter particle that has $W^{+}{W}^{-}$ as one of the major annihilation modes. Examples of such particles are supersymmetric particles with a dominant Higgsino component, or heavy triplet neutrinos. A substantial branching ratio is found for the $\gamma \gamma$ and $\gamma Z$ modes. We estimate the strength of the monoenergetic $\gamma$ ray lines that result from such annihilations in the Galactic or LMC halos. (Latex file; 2 compressed uuencoded postscript figures available by anonymous ftp from vanosf.physto.se in file pub/figures/lines.uu)

Comments: 11 pages, USITP-94-03; PAR-LPTHE 94-06