Projections for Dark Photon Searches at Mu3e

Abstract

We show that dark photons (A') with masses ~10-80 MeV can be probed in the decay ${\mu }^{+}\to e^{+}{\nu }_e{\bar{\nu }}_{\mu }{A}^{\prime },A^{\prime }\to e^{+}{e}^{-}$, with the upcoming Mu3e experiment at the Paul Scherrer Institute (PSI) in Switzerland. With an expected 10^{15} (5.5 x 10^{16}) muon decays in 2015-2016 (2018 and beyond), Mu3e has the exciting opportunity to probe a substantial fraction of currently unexplored dark photon parameter space, probing kinetic-mixing parameter, epsilon, as low as epsilon^2 ~ 10^{-7} (10^{-8}). No modifications of the existing Mu3e setup are required.

Comments: 9 pages, 7 figures; typos corrected, references added