Fermionic Semi-Annihilating Dark Matter

TL;DR

This paper explores semi-annihilating fermionic dark matter models with multi-component sectors, analyzing their phenomenology and potential to explain galactic gamma-ray excesses, while assessing detection prospects.

Contribution

It introduces minimal fermionic semi-annihilating dark matter models with SU(2)L singlet or triplet fermions and studies their phenomenology and experimental signatures.

Findings

Semi-annihilation can explain the galactic center gamma-ray excess.

Parameter space allows all observed dark matter to be detectable by current and future experiments.

Semi-annihilation effects significantly modify signals and constraints in these models.

Abstract

Semi-annihilation is a generic feature of dark matter theories with symmetries larger than Z2. We investigate two examples with multi-component dark sectors comprised of an SU(2)L singlet or triplet fermion besides a scalar singlet. These are respectively the minimal fermionic semi-annihilating model, and the minimal case for a gauge-charged fermion. We study the relevant dark matter phenomenology, including the interplay of semi-annihilation and the Sommerfeld effect. We demonstrate that semi-annihilation in the singlet model can explain the gamma ray excess from the galactic center. For the triplet model we scan the parameter space, and explore how signals and constraints are modified by semi-annihilation. We find that the entire region where the model comprises all the observed dark matter is accessible to current and planned direct and indirect searches.