Probing light axion-like particle via primordial black hole evaporation with gamma-ray observations

Abstract: The axion-like particle (ALP) and primordial black hole (PBH) are two representative dark matter (DM) candidates as light bosonic DM and macroscopic objects, respectively. In this work, we investigate the gamma-ray production mechanisms induced by PBH evaporation and ALP-photon coupling $g_{a\gamma\gamma}$. The detection of gamma-rays is also explored in future satellite telescopes, including AMEGO, e-ASTROGAM and MAST. We first propose the evaporation-conversion scenario in which light ALPs are emitted by PBHs and are converted into photons in the presence of magnetic field in the Universe. The second scenario assumes ALPs as dominant DM component in the Milky Way and considers the relativistic electron production from PBH evaporation. The emitted electrons scatter off non-relativistic ALP in DM halo and produce gamma-rays through the ALP-photon coupling. Using the Fisher forecasting method, we calculate the gamma-ray energy spectra from these two scenarios and derive projected sensitivity for the fraction of DM composed of PBHs $f_{\rm PBH}$ and ALP-photon coupling $g_{a\gamma\gamma}$.