Probing Ultra-light Primordial Black Holes as a Dark Matter Candidate

TL;DR

This paper reviews the potential of ultra-light primordial black holes as dark matter candidates, focusing on observational constraints, Hawking radiation emissions, and how future gamma-ray telescopes can test their viability.

Contribution

It provides a comprehensive overview of current constraints on ultra-light PBHs as dark matter and discusses how upcoming gamma-ray observations can further probe this candidate.

Findings

Ultra-light PBHs can emit detectable Hawking radiation.

Next-generation gamma-ray telescopes can set new limits on PBH dark matter.

Observational constraints significantly restrict the parameter space for ultra-light PBHs.

Abstract

Dark Matter (DM) is omnipresent in our universe. Despite its abundance, the microscopic identity of DM still remains a mystery. Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the early universe, are one of the earliest proposed and viable DM candidates. Recent studies indicate that PBHs can make up a large or even entire fraction of the DM density for a wide range of masses. Here, we briefly review the observational constraints on PBHs as DM, concentrating on the ultra-light mass window. Ultra-light PBHs emit particles via Hawking radiation and can be probed by observing such Hawking evaporated particles in various space as well as ground based detectors. We also outline how next-generation gamma ray telescopes can set a stringent exclusion limit on ultra-light PBH DM by probing low energy photons.