Bremsstrahlung in dark matter annihilation

TL;DR

This paper demonstrates that the energy spectra from dark matter annihilation into specific final states are identical across three different particle interaction scenarios, revealing underlying symmetries.

Contribution

It shows the equivalence of energy spectra in three dark matter models and calculates differential cross sections for additional processes, highlighting model-independent features.

Findings

Spectra are identical in three different DM interaction scenarios.

Differential cross sections depend on DM type but are independent of emitted boson V.

Results reveal symmetry properties in dark matter annihilation processes.

Abstract

We show that the energy spectra from dark matter (DM) annihilation into $f^+f^-\gamma$ (where $f$ is a light fermion) via chirality preserving interactions are identical in 3 scenarios: (a) DM is a Majorana fermion and the particle exchanged is a scalar, (b) DM is a Majorana fermion and the particle exchanged is a vector and (c) DM is a scalar and the particle exchanged is a fermion. For cases (a) and (c), we also calculate the differential cross section to $\ell^+f^-V$, where $V=W,Z,\gamma$, and $\ell$ is a light fermion that may or not be the same as $f$. The form of the cross section depends on whether the DM is a Majorana fermion or a scalar but in both cases its form is independent of $V$.