The HPS experiment: Searching for a dark photon at Jefferson Lab

Abstract

The Heavy Photon Search (HPS) experiment at Jefferson Laboratory will search for heavy U(1) vector bosons, called 'heavy photons' or 'dark photons'. Heavy photons are expected on very general theoretical grounds, and recent astrophysical evidence suggesting they might mediate dark matter annihilations and/or interactions with ordinary matter has motivated the search for a heavy photon in the mass range mA′∼20 to 1000 MeV/c2. Heavy photons couple to ordinary photons through kinetic mixing, which induces their weak coupling to electrons. Since they couple to electrons, heavy photons are radiated in electron scattering and can subsequently decay into narrow e+e− resonances which can be observed above the background. Using the high luminosity, precision electron beam available from Jefferson Lab and a combination of a silicon microstrip vertex tracker with a lead tungstate calorimeter, HPS will explore a large and unexplored domain in the mass/coupling plane with extraordinary sensitivity. This talk will review the motivations for the search for dark photons, and will present the experimental set-up and goals of the HPS experiment.