Exploring semi-relativistic $p$-wave dark matter annihilation in minimal Higgs portal near supermassive black hole

Abstract

We conduct a comprehensive analysis of potential annihilation processes of light dark matter (DM) in minimal Higgs portal models near supermassive black hole (Sgr A${}^{\star }$) in the Galactic Center, considering interactions between DM particles mediated by either a light scalar or pseudoscalar with couplings $c_s$ and $c_p$. Accelerated by the supermassive black hole, DM particles can reach velocities up to half the speed of light, significantly enhancing the $p$-wave annihilation cross-section, allowing forbidden annihilation channels within specific mass ranges, and producing unique gamma-ray spectral signals. Utilizing gamma-ray observation from Fermi Large Area Telescope (Fermi-LAT) in the direction of Sgr $A^{\star }$, we constrain light DM parameter in the mass range of $0.3-10\text{GeV}$ . Our results indicate that the couplings $c_s$ and $c_p$ are constrained to the order of $10^{-5}$, corresponding to a DM annihilation cross-section as low as $10^{-38}$${\mathrm{cm}}^3/\mathrm{s}$. In the future, the Very Large Gamma-ray Space Telescope (VLAST), with a larger detection area and broader detection range from $1$ MeV to $1$ TeV, will enhance our ability to probe sub-GeV DM and offer the opportunity to further study the forbidden annihilation scenario.

Comments: 28 pages,18 figures