Projections for dark photon searches at Mu3e

We show that dark photons (A ′) with masses ∼ 10-80 MeV can be probed in the decay μ⁺→ e⁺νₑν̄μA , A ′ → e + e −, with the upcoming Mu3e experiment at the Paul Scherrer Institute (PSI) in Switzerland. With an expected 1015 (5.5 × 1016) 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, ϵ, as low as ϵ 2 ∼ 10−7 (10−8). No modifications of the existing Mu3e setup are required.