Abstract
We present a model of weak scale dark matter (DM) where the thermal DM density is set by the lepton asymmetry due to the presence of higher dimension lepton violating operators. In these models there is generically a separation between the annihilation cross section responsible for the relic abundance (through lepton violating operators) and the annihilation cross section that is relevant for the indirect detection of DM (through lepton preserving operators). This implies a perceived boost in the annihilation cross section in the Galaxy today relative to that derived for canonical thermal freeze-out, giving a natural explanation for the observed cosmic ray electron and positron excesses, without resorting to a Sommerfeld enhancement. These models motivate continued searches for DM with apparently nonthermal annihilation cross sections. The DM may also play a role in radiatively generating Majorana neutrino masses.
- Received 30 September 2009
DOI:https://doi.org/10.1103/PhysRevLett.104.101301
©2010 American Physical Society
Synopsis
SynopsisA different way to look at dark matter
Published 11 March 2010
A model in which the dark matter relic density was inherited from the lepton asymmetry in the early universe can result in lepton-favoring dark matter annihilations today, which may explain recent anomalous cosmic-ray positron observations.
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