Dark Photons and Displaced Vertices at the MUonE Experiment

Abstract

MUonE is a proposed experiment designed to measure the hadronic vacuum polarization contribution to muon $g-2$ through elastic $\mu -e$ scattering. As such it employs an extremely high-resolution tracking apparatus. We point out that this makes MUonE also a very promising experiment to search for displaced vertices from light, weakly-interacting new particles. We demonstrate its potential by showing how it has excellent sensitivity to dark photons in the mass range $10\mathrm{MeV}\le m_{A^{\prime }}\le 100\mathrm{MeV}$ and kinetic mixing parameter $10^{-5}\le ϵe\le 10^{-3}$, through the process ${\mu }^{\pm }{e}^{-}\to {\mu }^{\pm }{e}^{-}{A}^{\prime }$ followed by $A^{\prime }\to e^{+}{e}^{-}$.

Comments: PRD version, 10 pages, 5 figures