Dark photons and displaced vertices at the MUonE experiment
Iftah Galon, David Shih, Isaac R. Wang
Abstract
MUonE is a proposed experiment designed to measure the hadronic vacuum polarization contribution to muon $g\ensuremath{-}2$ through elastic $\ensuremath{\mu}\ensuremath{-}e$ 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 $10\text{ }\text{ }\mathrm{MeV}\ensuremath{\le}{m}_{{A}^{\ensuremath{'}}}\ensuremath{\le}100\text{ }\text{ }\mathrm{MeV}$ and kinetic mixing parameter ${10}^{\ensuremath{-}5}\ensuremath{\le}\ensuremath{\epsilon}e\ensuremath{\le}{10}^{\ensuremath{-}3}$, through the process ${\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}{e}^{\ensuremath{-}}{A}^{\ensuremath{'}}$ followed by ${A}^{\ensuremath{'}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$.