Novel Constraints on Mixed Dark-Matter Scenarios of Primordial Black Holes and WIMPs

TL;DR

This paper establishes new, stringent constraints on the coexistence of primordial black holes and WIMPs as dark matter, based on WIMP density spikes and annihilation signals, surpassing previous bounds across a wide PBH mass range.

Contribution

It introduces novel constraints on mixed dark-matter models involving PBHs and WIMPs, considering WIMP density spikes and annihilation effects, improving upon prior bounds.

Findings

Stronger bounds on PBH fraction for masses 10^{-12} to 10^{4} solar masses.

Enhanced indirect detection prospects due to WIMP density spikes.

Constraints depend on WIMP mass and annihilation cross-section.

Abstract

We derive constraints on mixed dark-matter scenarios consisting of primordial black holes (PBHs) and weakly interacting massive particles (WIMPs). In these scenarios, we expect a density spike of the WIMPs that are gravitationally bound to the PBHs, which results in an enhanced annihilation rate and increased indirect detection prospects. We show that such scenarios provide strong constraints on the allowed fraction of PBHs that constitutes the dark matter, depending on the WIMP mass $m_{\chi}$ and the velocity-averaged annihilation cross-section $\langle \sigma v \rangle$. For the standard scenario with $m_{\chi} = 100\,{\rm GeV}$ and $\langle \sigma v \rangle = 3 \times 10^{-26}\,{\rm cm}^{3} / {\rm s}$, we derive bounds that are stronger than all existing bounds for PBHs with masses $10^{-12}\,M_{\odot} \lesssim M_{\rm BH} \lesssim 10^{4}\,M_{\odot}$, where $M_{\odot}$ is the solar mass, and mostly so by several orders of magnitude.