Axion-Like Particle Mediated Dark Matter and Neutron Star Properties in the QHD Model

Abstract: We investigate the effects of the ALP-mediated dark matter (DM) model on neutron star properties using the Quantum Hadrodynamics model (QHD). Using the relativistic mean-field approximation with the QHD-ALP-DM framework, we compute the equation of state (EoS) of neutron stars. Based on our previous study, we find that typical ALP parameter values have no significant effect on the EoS. We then explore various parametrizations of this model by varying the DM Fermi momentum, $q_f$, and DM mass, $m_{\chi}$. Our results show that increasing $q_f$ or $m_{\chi}$ shifts the energy density to higher values while reducing the maximum mass, radius, and tidal deformability of neutron stars. Finally, comparison with observational constraints from gravitational wave events and pulsar measurements indicates that the allowed parameter space for this model is constrained to $q_f < 0.05$ MeV and $m_{\chi} < 1000$ GeV. As a result, our study highlights the importance of next-generation gamma-ray observatories, such as the Cherenkov Telescope Array (CTA), in probing the ALP-mediated DM model.