Constraining dark matter interactions mediated by a light scalar with white dwarfs

Abstract

Observations of white dwarfs in dark matter-rich environments can provide strong limits on the strength of dark matter interactions. Here we apply the recently improved formalism of the dark matter capture rate in white dwarfs to a general model in which dark matter interacts with the white dwarf ion components via a light scalar mediator. We compute the dark matter capture rate in the optically thin limit in a cold white dwarf from the globular cluster Messier. We then estimate the threshold cross section, which significantly varies as a function of the light scalar mediator mass m_ϕ in the range of 0.05 m_χ<m_ϕ<m_χ and becomes constant when m_ϕ>m_χ. We also show that the bounds obtained from the dark matter capture in a white dwarf from the globular cluster Messier 4 are complementary to direct detection experiments and particularly strong in the sub-GeV regime.