Observable monochromatic photons from cosmic photino annihilation

Abstract

A recent suggestion that the observations of monochromatic photons from annihilation of photinos into quarkonium plus a photon could be a signature of dark-matter photinos is extended to include all S- and P-wave bound quarkonium states for a general interaction Lagrangian and an estimate of the cross sections is given. We also propose the process \ensuremath{\lambda}\ensuremath{\lambda}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma} as a potentially rich source of monochromatic photons and estimate its strength.