Constraining vector dark matter and dark photon with degenerate mass in a hidden local <i>SU</i>(2) model*

Abstract We discuss almost degenerate vector dark matter and dark photonsinduced from the hidden gauge sector, where it is spontaneously broken by the vacuum expectation value of doublet. Kinetic mixing between and gauge fields can be generated by introducing a dimension six operator realizing dark photon interactions. In estimating relic density, we focus on the process in which dark matter annihilates into dark photons and search for the region of dark matter mass and gauge coupling realizing observed relic density. We then discuss constraints from dark photon physics, thermalization of dark sector, and direct detection of dark matter. It is then found that constraints from direct detection experiments give us the strongest upper limits on the dark photon interactions.