Improved treatment of dark matter capture in neutron stars III: nucleon and exotic targets

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.

Capture of Electroweak Multiplet Dark Matter in Neutron Stars

“…[56] in the horizontal dotted line and σ (n) th 1.4 × 10 −44 cm 2 obtained in Ref. [59] in the horizontal solid line. In the latter, the effect of large momentum transfer and effective nucleon mass in NSs is taken into account.…”

“…This formula is valid in the limit of zero momentum transfer. This is a fairly good approximation for the evaluation of the DM direct detection rate, but may be modified by a factor of ∼ 10 for the scattering in NSs [58,59]. 14 We also have the dimension-six operator of the form…”

Neutron Star Heating in Dark Matter Models for the Muon $g-2$ Discrepancy

“…In the models presented in this work, DM particles predominantly interact with nucleons and muons. The threshold cross sections for the interaction with such particles are estimated to be σ N th [1.7 × 10 −45 , 1.4 × 10 −44 ] cm 2 and σ µ th 8 × 10 −44 cm 2 for the case of interactions with neutrons [126,128] and muons [127] respectively. In this work, we regard these results as representative values.…”

“…8 We also show the threshold cross section for DM interactions with neutron obtained in Refs. [126,128], σ th [1.7 × 10 −45 , 1.4 × 10 −44 ] cm 2 , in the horizontal red band. As seen from these plots, the SD scattering cross sections are predicted to be smaller than the XENON1T limit [170] in the parameter regions where the muon g − 2 discrepancy can be explained.…”

“…The horizontal red band represents the threshold cross section for neutron obtained in Refs. [126,128]…”