Bayesian exploration of weakly interacting models of dark matter admixed neutron stars based on multi-density constraints

We present a unified Bayesian analysis of Higgs-portal, neutron-decay, and axion-like-particle (ALP)-mediated dark matter in neutron stars within the single-fluid approximation. Using a common relativistic mean-field description of hadronic matter, we combine finite-nucleus and heavy-ion collision data, chiral effective field theory, NICER measurements of four pulsars, and GW170817. The individual dark-sector parameters remain weakly determined, while model-dependent shifts in nuclear skewness reveal the sensitivity of the inferred hadronic equation of state to the assumed dark-matter mechanism. The three scenarios yield substantially overlapping mass-radius and tidal-deformability predictions, with median maximum masses near 2.1,M. For 1.4,M stars, the Higgs-portal model predicts higher f-mode frequencies and shorter damping times than the neutron-decay and ALP models, although their credible regions overlap. Comparison with three consistently reanalysed two-fluid models gives the largest Bayesian evidence to neutron decay: under the adopted priors, its Bayes factors relative to the Higgs-portal and two-fluid alternatives are approximately 24 - 37, but only 2.2 relative to ALP. This ranking concerns complete dark-matter models and does not establish a general preference for either fluid description or evidence for a dark component itself. Improved nuclear constraints and future gravitational-wave asteroseismology could provide complementary information to disentangle the hadronic and dark-sector contributions.