New Analysis of Neutron Star Constraints on Asymmetric Dark Matter
  Due to their extreme density and low temperature, neutron stars (NS) are
efficient probes to unveil interactions between standard model and dark matter
(DM) particles. From elastic scatterings on NS material, DM can get
gravitationally trapped by the star. The cooling of DM through further
collisions may lead to the formation of a dense core which could collapse into
a black hole, thus destroying the whole NS. From the observation of old NS,
such a scenario leads to very stringent constraints on the parameter space of
asymmetric DM. In this work we reexamine this possibility in detail. This
includes: (a) a new detailed determination of the number of DM particles
captured, properly taking into account the fact that neutrons form a highly
degenerate Fermi material; (b) the determination of the time evolution of the
DM density and energy profiles inside the NS, which allows us to understand
how, as a function of time, DM thermalizes with NS material; (c) the
determination of the corresponding constraints which hold on the DM-neutron
cross section, including for the case where a large fraction of DM particles
have not thermalized; (d) the first determination of the stringent constraints
which also hold in a similar way on the DM-muon cross section, particularly
relevant for leptophilic DM models; and (e) the use of realistic NS equations
of state in determining these constraints.
