Sensitivity of future lepton colliders to the search for charged lepton flavor violation

Abstract

The observation of lepton flavor violation indicates new physics beyond the Standard Model. Lepton colliders are ideal facilities to probe charged lepton flavor violation (CLFV) signals induced by new physics at high energy. We perform a comprehensive study of the sensitivity of future lepton colliders to charged lepton flavor violation. We consider the most general renormalizable Lagrangian coupling two leptons to new bosonic particles, involving both $\mathrm{\ensuremath{\Delta}}L=0$ and $\mathrm{\ensuremath{\Delta}}L=2$ interactions. The CLFV processes are introduced by the exchange of off-shell new particles at tree level. We find that CEPC, ILC, FCC-ee, and CLIC each provide a complementary probe of CLFV couplings to low-energy precision experiments for $\ensuremath{\tau}$ lepton(s) in final states, while low-energy precision experiments are more sensitive in the absence of $\ensuremath{\tau}$ leptons.