Dark Higgs dark matter
Cristina Mondino, Maxim Pospelov, Joshua T. Ruderman, Oren Slone
Abstract
A new $U(1)$ ``dark'' gauge group coupled to the Standard Model (SM) via the kinetic mixing portal provides a dark matter candidate in the form of the Higgs field, ${h}_{d}$, responsible for generating the mass of the dark photon, ${\ensuremath{\gamma}}_{d}$. We show that the condition ${m}_{{h}_{d}}\ensuremath{\le}{m}_{{\ensuremath{\gamma}}_{d}}$, together with smallness of the kinetic mixing parameter, $\ensuremath{\epsilon}$, and/or dark gauge coupling, ${g}_{d}$, leads the dark Higgs to be sufficiently metastable to constitute dark matter. We analyze the Universe's thermal history and show that both freeze-in, $\mathrm{SM}\ensuremath{\rightarrow}{{\ensuremath{\gamma}}_{d},{h}_{d}}$, and freeze-out, ${{\ensuremath{\gamma}}_{d},{h}_{d}}\ensuremath{\rightarrow}\mathrm{SM}$, processes can lead to viable dark Higgs dark matter with a sub-GeV mass and a kinetic mixing parameter in the range ${10}^{\ensuremath{-}13}\ensuremath{\lesssim}\ensuremath{\epsilon}\ensuremath{\lesssim}{10}^{\ensuremath{-}6}$. Observable signals in astrophysics and cosmology include modifications to primordial elemental abundances, altered energetics of supernovae explosions, dark Higgs decays in the late Universe, and dark matter self-interactions.