Enhanced One-Loop Corrections to WIMP Annihilation and their Thermal Relic Density in the Coannihilation Region

TL;DR

This paper calculates one-loop quantum corrections to WIMP co-annihilation processes, focusing on Sommerfeld effects, and provides analytical expressions to improve predictions of dark matter relic density, especially for wino- or higgsino-like neutralinos.

Contribution

It introduces exact analytical formulas for Sommerfeld corrections in co-annihilation, accounting for mass splittings and mixing effects, advancing precision in dark matter relic density calculations.

Findings

Corrections can significantly alter co-annihilation cross sections.

Mass splittings impact loop functions and correction magnitudes.

Analytical expressions are derived for specific neutralino cases.

Abstract

We consider quantum corrections to co-annihilation processes of Weakly Interacting Massive Particles (WIMPs) due to the exchange of light bosons in the initial state ("Sommerfeld corrections"). We work at one-loop level, i.e. we assume that these corrections can be treated perturbatively. Co-annihilation is important if there is at least one additional new particle with mass close to the lightest WIMP, which is a Dark Matter candidate. In this case the exchange of a (relatively light) boson in the initial state can change the identity of the annihilating particles. The corrections we are interested in factorize, as in the case of WIMP self-annihilation treated previously, but they can mix different tree-level amplitudes. Moreover, even small mass splittings between the external particles and those in the loop can change the relevant loop functions significantly. We find exact analytical expressions for these functions, and illustrate the effects by considering the cases of wino- or higgsino-like neutralinos as examples.