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

TL;DR

Future lepton colliders like CEPC, ILC, FCC-ee, and CLIC can effectively probe charged lepton flavor violation, providing complementary sensitivity to low-energy experiments, especially involving tau leptons, through off-shell new particle exchanges.

Contribution

This study offers a comprehensive analysis of the sensitivity of upcoming lepton colliders to charged lepton flavor violation using a general renormalizable Lagrangian framework.

Findings

Lepton colliders can probe CLFV couplings at high energies.

Complementary sensitivity between colliders and low-energy experiments.

Enhanced detection prospects for tau-involving CLFV processes.

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. In this work 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 $\Delta L=0$ and $\Delta L=2$ 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 $\tau$ lepton(s) in final states, while low-energy precision experiments are more sensitive in the absence of $\tau$ leptons.