On the likely dominance of WIMP annihilation to f(bar sign)f+W/Z (and implication for indirect detection)
- Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 (United States)
Arguably, the most popular candidate for Dark Matter (DM) is a massive, stable, Majorana fermion. However, annihilation of Majorana DM to two fermions features a helicity-suppressed s-wave rate. Radiating a gauge boson via electroweak (EW) and electromagnetic (EM) bremsstrahlung removes this s-wave suppression. The main purpose of this talk is to explain in some detail why the branching ratio Br({yields}f(bar sign)f) is suppressed while Br({yields}f(bar sign)f+W/Z/{gamma}) is not. In doing so, we investigate the general conditions for s-wave suppression and un-suppression using Fierz transformations and partial wave expansions. Suppression for the 2 {yields} 2 process is sufficiently severe that the EW and EM bremsstrahlung are likely to be the dominant modes of gauge-singlet Majorana DM annihilation. We end this talk with a discussion of the challenge presented by space-based data for Majorana DM models, given that the enhanced rate to radiated W and Z gauge bosons and their dominant decay via hadronic channels tends to produce more antiprotons than are observed.
- OSTI ID:
- 22118504
- Journal Information:
- AIP Conference Proceedings, Vol. 1534, Issue 1; Conference: CETUP 2012: Workshop on dark matter, unification and neutrino physics, Lead-Deadwood, SD (United States), 10 Jul - 1 Aug 2012; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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