Capture of Electroweak Multiplet Dark Matter in Neutron Stars

Abstract

If dark matter has a sizable scattering cross section with nucleons, it can efficiently be captured by a neutron star. Its energy is then transferred to the neutron star as heat through the scattering and annihilation inside the star. This heating effect may be detectable via dedicated temperature observations of nearby old pulsars, providing an alternative method for dark matter searches. In this paper, we show that for electroweak multiplet dark matter this search strategy can probe the parameter region which is out of reach of future dark matter direct detection experiments. To see this systematically, we classify such dark matter candidates in terms of their electroweak charges and investigate the effect of ultraviolet physics by means of higher-dimensional effective operators. We then show that if the effect of ultraviolet physics is sizable, the dark matter-nucleon elastic scattering cross section becomes sufficiently large, whilst if it is suppressed, then the mass splittings among the components of the DM multiplet get small enough so that the inelastic scattering processes are operative. In any case, the electroweak multiplet dark matter particles are efficiently captured in neutron stars, making the search strategy with the temperature observation of old neutron stars promising.

Neutron star observations of pseudoscalar-mediated dark matter

“…In particular, this indirect probe is sensitive to many types of particle-like DM that are challenging to detect through direct scattering in the laboratory. This includes lighter sub-GeV DM [22,28,36,38,39], DM that scatters primarily inelastically [19,22,24,41], and scenarios where the scattering rate of DM with nuclei is suppressed by positive powers of the DM velocity [21,36,39].…”

Faint light of old neutron stars from dark matter capture and detectability at the James Webb Space Telescope

“…In the local bubble, NS older than Gyrs can have an increase in temperature from about ∼ 100 K to ∼ 2000 K due to DM heating mechanisms [17,19]. Observation of such NS would place constraints on DM mass and their interaction strength with visible matter in a broadly model independent way [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”