Interest in the possibility that a massive photon-like particle could exist and play a role in dark matter annihilation emerged in 2009, and has generated considerable activity since then. Such a particle is natural on very general theoretical grounds and could account for the striking evidence of an excess of high energy electrons and a rising positron fraction in the cosmic rays. A heavy photon could account for dark matter interactions with regular matter, and so bear on dark matter direct detection experiments.
The heavy photon can be produced in electron bremsstrahlung off heavy targets, albeit at rates strongly suppressed compared to production of virtual photons of the same mass. The signatures for a heavy photon would be a bump in the e+e− invariant mass and a secondary decay vertex. Jefferson Lab is home for three experiments for heavy photon searches, DarkLight, APEX and HPS. The APEX experiment in Hall-A already published their first results, and HPS in Hall-B just concluded part of the engineering run. In this talk, status of the heavy photon searches and the experiments at Jefferson Lab will be discussed.
Argonne Physics Division Seminar Schedule