Probing the $L_\mu$-$L_\tau$ Gauge Boson at the MUonE Experiment

Understand

We discuss the prospects of probing the $L_\mu - L_\tau$ gauge boson at the MUonE experiment.

• The $L_\mu - L_\tau$ gauge boson $Z^\prime$ with a mass of $\lesssim 200$ MeV, which can explain the discrepancy between the measured value of the muon $g-2$ and the value calculated in the Standard Model, can be produced at the MUonE experiment through the process $\mu e \to \mu e Z^\prime$.
• The $Z^\prime$ in the final state decays into a pair of neutrinos, and therefore we cannot observe the decay of $Z^\prime$ directly.
• It is, however, still possible to probe this signature by searching for events with a large scattering angle of muon and a less energetic final-state electron.