We propose a new mechanism for thermal dark matter freeze-out, called codecaying dark matter. Multicomponent dark sectors with degenerate particles and out-of-equilibrium decays can codecay to obtain the observed relic density. The dark matter density is exponentially depleted through the decay of nearly degenerate particles rather than from Boltzmann suppression. The relic abundance is set by the dark matter annihilation cross section, which is predicted to be boosted, and the decay rate of the dark sector particles. The mechanism is viable in a broad range of dark matter parameter space, with a robust prediction of an enhanced indirect detection signal. Finally, we present a simple model that realizes codecaying dark matter.
Bibliographical noteFunding Information:
We thank Marco Farina for collaboration in the early stages of the project. We are grateful to Spencer Chang, Tim Cohen, Graham Kribs, Michelle Papucci, Tracy Slatyer, and Hitoshi Murayama for useful discussions. We especially thank Yonit Hochberg for useful discussions and comments on the manuscript. This work was supported in part by the National Science Foundation (NSF) through Grant No. PHY-1316222. J. D. is supported in part by the National Science and Engineering Research Council of Canada (NSERC) Grant No. PGSD3-438393-2013. E. K. is supported by a Hans Bethe Postdoctoral Fellowship at Cornell.
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