Improved Treatment of Dark Matter Capture in Neutron Stars III: Nucleon and Exotic Targets

TL;DR

This paper improves the modeling of dark matter capture in neutron stars by including hadronic structure effects and baryon interactions, revealing suppressed capture rates and enhanced detection sensitivity over previous models.

Contribution

It introduces momentum-dependent form factors and baryon interactions into dark matter capture calculations, providing more accurate estimates especially for exotic matter in neutron stars.

Findings

Capture rate suppression over a wide mass range

Reduced variability due to neutron star equation of state

Enhanced sensitivity for dark matter detection compared to nuclear recoil experiments

Abstract

We consider the capture of dark matter (DM) in neutron stars via scattering on hadronic targets, including neutrons, protons and hyperons. We extend previous analyses by including momentum dependent form factors, which account for hadronic structure, and incorporating the effect of baryon strong interactions in the dense neutron star interior, rather than modelling the baryons as a free Fermi gas. The combination of these effects suppresses the DM capture rate over a wide mass range, thus increasing the cross section for which the capture rate saturates the geometric limit. In addition, variation in the capture rate associated with the choice of neutron star equation of state is reduced. For proton targets, the use of the interacting baryon approach to obtain the correct Fermi energy is essential for an accurate evaluation of the capture rate in the Pauli-blocked regime. For heavy neutron stars, which are expected to contain exotic matter, we identify cases where DM scattering on hyperons contributes significantly to the total capture rate. Despite smaller neutron star capture rates, compared to existing analyses, we find that the projected DM-nucleon scattering sensitivity greatly exceeds that of nuclear recoil experiments for a wide DM mass range.