Searches for the dark photon at fixed target experiments

Abstract

Recent astrophysical observations provided indirect evidences for sub-GeV, light, dark-matter (DM). A new gauge particle in this mass range could exist as an extra U(1) gauge particle, called the dark photon. The dark photon can mix weakly with a ordinary photon and can mediate interactions of DM. If the dark photon is massive enough, it can decay into a pair of standard-model (SM) particles or DM particles. Light dark-matter particles in the MeV to GeV mass range, as well as in other mass ranges, have not been the subjects of intensive experimental researches. Large statistics is needed to search for dark-photon-mediated interactions. Therefore, high-power accelerators can be used to look for the dark photon. In this article, we review the current status of the experimental searches at various fixed-target experiments and the experiments planned in the near term future. © 2016, Korean Physical Society. All rights reserved.