Searching Accretion-Enhanced Dark Matter Annihilation Signals in the Galactic Centre

TL;DR

This paper investigates velocity-dependent dark matter annihilation signals near the Galactic Center, analyzing gamma-ray data to identify potential signatures of resonance and forbidden processes within a detailed fermionic DM model.

Contribution

It introduces a comprehensive analysis of velocity-dependent DM annihilation processes, incorporating a fermionic model with an electroweak ALP portal and precise flux calculations near Sgr A*.

Findings

Resonance and forbidden annihilation scenarios can produce detectable gamma-ray lines.

Upper limits on the ALP-DM-DM coupling constant were established.

Velocity and positional dependencies significantly influence gamma-ray flux predictions.

Abstract

This study reanalyzes the detection prospects of dark matter (DM) annihilation signals in the Galactic Center, focusing on velocity-dependent dynamics within a spike density near the supermassive black hole (Sgr~A$^{\star}$). We investigate three annihilation processes -- $p$-wave, resonance, and forbidden annihilation -- under semi-relativistic velocities, leveraging gamma-ray data from Fermi and DAMPE telescopes. Our analysis integrates a fermionic DM model with an electroweak axion-like particle (ALP) portal, exploring annihilation into two or four photons. Employing a comprehensive six-dimensional integration, we precisely calculate DM-induced gamma-ray fluxes near Sgr~A$^{\star}$, incorporating velocity and positional dependencies in the annihilation cross-section and photon yield spectra. Our findings highlight scenarios of resonance and forbidden annihilation, where the larger ALP-DM-DM coupling constant $C_{a\chi\chi}$ can affect spike density, potentially yielding detectable gamma-ray line spectra within Fermi and DAMPE energy resolution. We set upper limits for $C_{a\chi\chi}$ across these scenarios, offering insights into the detectability and spectral characteristics of DM annihilation signals from the Galactic Center.