Proto-neutron stars as cosmic factories for massive axion-like-particles

TL;DR

This paper explores the potential of proto-neutron stars to produce heavy axion-like particles (ALPs) with masses around 100 MeV, providing new constraints and insights into their production and decay mechanisms.

Contribution

It introduces the first detailed characterization of heavy ALP emission from proto-neutron stars, including mass effects in key production processes and new ways to probe ALP couplings through supernova observations.

Findings

New constraints on heavy ALPs with ~100 MeV mass.

Inclusion of mass effects in nucleon-nucleon Bremsstrahlung and pionic Compton processes.

Potential to probe ALP couplings via supernova ALP decay signatures.

Abstract

The parameter space of massive axion-like-particles (ALPs) with $m_a \sim {\mathcal O} (100)$ MeV and coupled with nucleons is largely unexplored. Here, we present new constraints in this parameter region. In doing so, we characterize the supernova emissivity of heavy ALPs from a proto-neutron star, including for the first time mass effects in both nucleon-nucleon Bremsstrahlung and pionic Compton processes. In addition, we highlight novel possibilities to probe the couplings with photons and leptons from supernova ALP decays.