Sho Uemura (Stanford) "The Heavy Photon Search Experiment at Jefferson Lab"

Abstract:
The Heavy Photon Search (HPS) is a new experiment at Jefferson Lab searching for massive U(1) vector bosons (also known as heavy photons, dark photons, or A prime with a weak effective coupling to electric charge. The heavy photon is motivated as part of a hidden sector” model of dark matter, where it would mediate the self-interaction of dark matter and the interaction of dark and ordinary matter. HPS is sensitive to heavy photons of mass 10-500 MeV with coupling strength episilon squared of 1e-5 to 1e-10. The HPS experiment is designed to produce heavy photons in a process analoguous to bremsstrahlung using an electron beam on a fixed target, and detect decays to e+e pairs with two signatures (invariant mass resonance and displaced decay vertex). The detector is a compact, large-acceptance forward spectrometer comprising a silicon microstrip tracker for momentum measurement and vertexing and an electromagnetic calorimeter for triggering on e+e. Precise beamline controls, high-rate trigger and DAQ, and good time resolution are needed for a detector that comes within 0.5 mm of the beam and is sensitive down to 15 mrad from the beam plane, and must cope with the intense beam background in this environment. A low-mass tracker and clean track reconstruction are needed for the best sensitivity. This talk will describe the HPS experiment and its current status after test, commissioning, and engineering runs.