Gamma-ray Signal from $Z_{N\geq 3}$ Dark Matter-Companion Models

TL;DR

This paper investigates gamma-ray signals from Z_{N≥3} dark matter models, analyzing indirect detection prospects and current experimental constraints, especially focusing on the spectral features and cross section limits.

Contribution

It introduces a detailed analysis of gamma-ray spectra from Z_{N≥3} dark matter models, including indirect detection signals and experimental bounds, expanding on previous semi-annihilation frameworks.

Findings

Hard gamma-ray spectrum mainly shaped by direct Higgs boson emission.

Current Fermi-LAT data constrains light dark matter cross sections to thermal levels.

Cherenkov Telescope Array can exclude most TeV-scale dark matter parameter space.

Abstract

In Ref.~\cite{Guo:2021rre}, we proposed to replace the final dark matter (DM) particle in the semi-annihilation mode $\rm DM+DM\to antiDM+Higgs~boson$ with its $Z_{N\geq 3}$ companion, thus reducing DM number density without DM-nucleon scattering. In this work, we study the indirect detection signals from DM annihilation, the Higgs boson pair with one of them from the companion decay being on- or off- shell, depending on the DM-companion mass splitting. We generate the photon spectrum by using PYTHIA8 and study the properties of the spectrum, to find that the hard part of the spectrum in our model is mainly shaped by the direct Higgs boson and thus does not differ much from that of the conventional semi-annihilation mode. Using the Fermi-LAT data of white dwarfs, we derive the current limit of the DM annihilation cross section for ${\rm DM+DM\to companion^*+Higgs~ boson}$, and for the relatively light DM, it reaches the typical thermal cross section. However, for the TeV scale DM, we have to rely on the Cherenkov Telescope Array, which is able to rule out the whole parameter space except for the coannihilation region.