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

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.
Comment: 14 pages, 7 figures. Matches the version to appear on PRD. Changes: contribution of the delta-mediated diagram in Pionic Compton processes added. Improvements in the treatment of the pion abundance inside the SN core, by taking the pion fraction and the pion chemical potential from the SN model employed