Improved constraints on dark matter annihilations around primordial black holes

A bstract 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 Ω DM ≈ 0.26. Early studies highlighted that scenarios with both particle dark matter and PBH are strongly excluded by γ -ray limits for particle dark matter with a velocity independent thermal cross section 〈 σν 〉 ~ 3 × 10 −26 cm 3 /s, as is the case for classic WIMP dark matter. Here we examine the limits from di use γ -rays on velocity-dependent, including annihilations which are p -wave with 〈 σν 〉 ∝ v 2 or d -wave 〈 σν 〉 ∝ v 4 , which we find to be considerably less constraining. This work also utilizes 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 γ -ray flux from the PBH halo.