Probing Double-Peaked Gamma-Ray Spectra from Primordial Black Holes with Next-Generation Gamma-Ray Experiments

TL;DR

This paper investigates the potential for future gamma-ray telescopes to detect double-peaked spectra from primordial black holes, which could confirm their role as dark matter or constrain their abundance.

Contribution

It introduces a likelihood-based method to distinguish double-peaked from single-peaked PBH gamma-ray spectra in next-generation observations.

Findings

Future gamma-ray experiments can identify double-peaked PBH spectra.

Spectral shape analysis can differentiate PBH mass distribution scenarios.

Constraints on PBH abundance are achievable through spectral features.

Abstract

Primordial black holes (PBHs), hypothesized to form in the early universe from gravitational collapse of density fluctuations, represent a well-motivated dark matter (DM) candidate. Their potential detection through gamma-ray signatures arising from Hawking radiation would provide definitive evidence for their existence and constrain their contribution to the DM abundance. Unlike conventional DM candidates, PBHs emit a unique, thermal-like spectrum of particles as they evaporate, including photons, neutrinos, and possible beyond-the-Standard Model particles. Future high-sensitivity gamma-ray observatories, such as e-ASTROGAM and other next-generation telescopes, will play a pivotal role in this search. With improved energy resolution and sensitivity, these missions can disentangle PBH-originating photons from astrophysical backgrounds, probe subtle spectral features such as multi-peak structures, and test exotic evaporation models. Such observations could either confirm PBHs as a viable DM component or place stringent limits on their abundance across critical mass windows. In this work, we explore the distinguishing features of a double-peaked gamma-ray spectrum produced by PBHs, focusing on the asteroid-mass window ($10^{15}$ g to $10^{17}$ g), where Hawking radiation peaks in the MeV to GeV range. Using a likelihood-based analysis, we demonstrate how future missions could discriminate between single- and double-peaked PBH scenarios, the latter arising in cosmological models predicting multi-modal PBH mass distributions. Our results highlight the diagnostic power of spectral shape analysis in identifying PBH populations and constrain the parameter space for which a double-peaked signal could be detectable above background.