Speaker
Description
Cosmology may give rise to appreciable populations of both particle dark matter and primordial black holes (PBH) with the combined mass density providing the observationally inferred value $\Omega_{\rm DM}\approx0.26$. Early studies highlighted that scenarios with both particle dark matter and PBH are strongly excluded by $\gamma$-ray limits for particle dark matter with a velocity independent thermal cross section $\langle\sigma v\rangle\sim3\times10^{-26}{\rm cm}^3/{\rm s}$, as is the case for classic WIMP dark matter. Here we examine the limits from diffuse $\gamma$-rays on velocity-dependent, including annihilations which are $p$-wave with $\langle\sigma v \rangle\propto v^2$ or $d$-wave $\langle\sigma v \rangle\propto v^4$, which we find to be considerably less constraining. This work also utilyses a refined treatment of the PBH dark matter density profile. Importantly, we highlight that even if the freeze-out process is $p$-wave it is typical for (loop/phase-space) suppressed $s$-wave processes to actually provide the leading contributions to the experimentally constrained $\gamma$-ray flux from the PBH halo.
