Electroweak Bremsstrahlung in Dark Matter Annihilation

Abstract

A conservative upper bound on the total dark matter (DM) annihilation rate can be obtained by constraining the appearance rate of the annihilation products which are hardest to detect. The production of neutrinos, via the process $\chi \chi \to \bar{\nu }\nu$, has thus been used to set a strong general bound on the dark matter annihilation rate. However, Standard Model radiative corrections to this process will inevitably produce photons which may be easier to detect. We present an explicit calculation of the branching ratios for the electroweak bremsstrahlung processes $\chi \chi \to \bar{\nu }\nu Z$ and $\chi \chi \to \bar{\nu }eW$. These modes inevitably lead to electromagnetic showers and further constraints on the DM annihilation cross-section. In addition to annihilation, our calculations are also applicable to the case of dark matter decay.

7 pages, 4 figures. New appendix with an extensive discussion of Majorana fermions and helicity suppressions

References in corpus (7)

• New Gamma-Ray Contributions to Supersymmetric Dark Matter Annihilation
• Evidence Of Dark Matter Annihilations In The WMAP Haze
• Neutrino Constraints on the Dark Matter Total Annihilation Cross Section
• Model-Independent Bound on the Dark Matter Lifetime
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Cited by in corpus (1)

• Muon Fluxes From Dark Matter Annihilation