Semi-Annihilating Wino-Like Dark Matter

TL;DR

This paper investigates a Z_4-symmetric dark matter model with a scalar singlet and a wino-like fermion triplet, analyzing semi-annihilation effects, Sommerfeld enhancement, and implications for relic density and detection constraints.

Contribution

It introduces the minimal semi-annihilating dark matter model with a gauge-charged fermion and studies its phenomenology including relic density and detection prospects.

Findings

Semi-annihilation modifies relic density calculations.

Sommerfeld effect impacts annihilation and semi-annihilation channels.

Model parameters can account for all observed dark matter within current detection limits.

Abstract

Semi-annihilation is a generic feature of dark matter theories with symmetries larger than Z_2. We explore a model based on a Z_4-symmetric dark sector comprised of a scalar singlet and a "wino"-like fermion SU(2)_L triplet. This is the minimal example of semi-annihilation with a gauge-charged fermion. We study the interplay of the Sommerfeld effect in both annihilation and semi-annihilation channels. The modifications to the relic density allow otherwise-forbidden regions of parameter space and can substantially weaken indirect detection constraints. We perform a parameter scan and find that the entire region where the model comprises all the observed dark matter is accessible to current and planned direct and indirect searches.