Dark matter capture in celestial objects: light mediators, self-interactions, and complementarity with direct detection

TL;DR

This paper extends the formalism for dark matter capture in celestial objects to include light mediators, showing that astrophysical constraints weaken significantly for light mediators and are complemented by terrestrial detection bounds, with implications for black hole formation.

Contribution

It generalizes DM capture formalism to arbitrary mediator masses and analyzes the impact on astrophysical and terrestrial constraints, including the effects of self-interactions and black hole formation.

Findings

Astrophysical constraints weaken for mediators lighter than 5 MeV (asymmetric DM) and 0.25 MeV (annihilating DM).

Terrestrial direct detection bounds become more relevant for small or large DM masses.

Self-interactions have minimal impact on capture rate but affect black hole formation criteria.

Abstract

We generalize the formalism for DM capture in celestial bodies to account for arbitrary mediator mass, and update the existing and projected astrophysical constraints on DM-nucleon scattering cross section from observations of neutron stars. We show that the astrophysical constraints on the DM-nucleon interaction strength, that were thought to be the most stringent, drastically weaken for light mediators and can be completely voided. For asymmetric DM, existing astrophysical constraints are completely washed out for mediators lighter than 5 MeV, and for annihilating DM the projected constraints are washed out for mediators lighter than 0.25 MeV. Related terrestrial direct detection bounds also weaken, but in a complementary fashion; they supersede the astrophysical capture bounds for small or large DM mass, respectively for asymmetric or annihilating DM. Repulsive self-interactions of DM have an insignificant impact on the total capture rate, but a significant impact on the black hole formation criterion. This further weakens the constraints on DM-nucleon interaction strength for asymmetric self-repelling DM, whereas constraints remain unaltered for annihilating self-repelling DM. We use the correct Hawking evaporation rate of the newly formed black hole, that was approximated as a blackbody in previous studies, and show that, despite a more extensive alleviation of collapse as a result, the observation of a neutron star collapse can probe a wide range of DM self-interaction strengths.