Constraining the scalar singlet and inert dark matter models using neutron stars

We study the scalar singlet as well as the two-Higgs doublet model inert dark matter particles’ impact on compact objects, and we provide the first constraints of the parameter space using neutron stars. The models discussed here are characterized by two free parameters, namely the mass Mχ of the scalar particle that plays the role of the dark matter in the Universe, and a dimensionless coupling constant λχ that determines the strength of the interaction of the dark matter particles with the Standard Model Higgs boson. By considering a typical neutron star we are able to obtain constraints on scalar dark matter depending on the dark matter (DM) annihilation cross section and self-interaction coupling constant. Our findings show that (i) for heavy DM particles neutron stars can provide us with bounds better that the current limits from direct detection searches only when the self-annihilations of DM particles are negligible and the DM self-interaction coupling constant is very small, while (ii) for light DM particles the bounds obtained here are comparable to limits from Higgs invisible decays unless the DM particles are extremely light.