Probing charged lepton flavor violation in an economical muon on-target experiment

This work proposes a novel and cost-effective experiment to probe the charged lepton flavor violation (CLFV) process mediated by an extra massive neutral gauge boson [Formula: see text] beyond the Standard Model, by extending a recently proposed muon dark matter project in the Peking University Muon (PKMuon) Experiment. The devices originally designed for light mass dark matter direct detection can be easily adapted to search for the [Formula: see text] CLFV process by leveraging the large-area, high-precision muon tracking and tomography system which sandwiches a fixed target that the incoming muons scatter off. The [Formula: see text] final state signal studied in this work can exclusively probe the muon-related coupling, thus uniquely sensitive to specific CLFV parameter combinations, such as the coupling coefficient product [Formula: see text]. A resampling method is developed to optimize beam propagation in detector simulations where the event generator for injected physics is originally designed for fixed particle energies. Prospective results are obtained through detailed detector simulations interfacing with a muon beam with energies in the tens of GeV and a flux of [Formula: see text]. Based primarily on the angular information of the incoming and outgoing particles, the expected upper limit at 95% confidence level on [Formula: see text] can reach [Formula: see text] with, for example, a [Formula: see text] mass of [Formula: see text] for a one-year run.