On the effective operators for Dark Matter annihilations

TL;DR

This paper systematically classifies effective operators for dark matter annihilation, focusing on non-relativistic regimes and electroweak bremsstrahlung effects, providing insights relevant for indirect detection strategies.

Contribution

It introduces a comprehensive set of dimension-8 operators that account for electroweak bremsstrahlung lifting helicity suppression in dark matter annihilation.

Findings

Constructed all relevant dimension-8 operators for DM annihilation.

Analyzed velocity dependence of operators for s- and p-wave processes.

Provided a framework for improved indirect DM search interpretations.

Abstract

We consider effective operators describing Dark Matter (DM) interactions with Standard Model fermions. In the non-relativistic limit of the DM field, the operators can be organized according to their mass dimension and their velocity behaviour, i.e. whether they describe s- or p-wave annihilations. The analysis is carried out for self-conjugate DM (real scalar or Majorana fermion). In this case, the helicity suppression at work in the annihilation into fermions is lifted by electroweak bremsstrahlung. We construct and study all dimension-8 operators encoding such an effect. These results are of interest in indirect DM searches.