Lepton Flavor Violation at FCC-ee and CEPC

TL;DR

This paper investigates the potential to detect lepton flavor violation at future electron-positron colliders, showing that these experiments can provide complementary constraints to existing low-energy measurements.

Contribution

It analyzes lepton flavor violating processes within the Standard Model Effective Field Theory at future colliders, highlighting their sensitivity and complementarity to low-energy experiments.

Findings

FCC-ee and CEPC can set competitive bounds on lepton flavor violation.

Future colliders provide complementary constraints to tau decay experiments.

Analysis covers on- and off-Z-pole energies.

Abstract

Lepton flavor violating processes are highly suppressed in the Standard Model. Therefore, if observed, lepton flavor violation would be a clear indication of new physics beyond the Standard Model. We study the process $e^+e^-\to\tau\mu$ at tree-level in the Standard Model Effective Field Theory both on the $Z$-pole and at higher center-of-mass energies. We show that the constraints derived from the future circular $e^+e^-$ colliders FCC-ee and CEPC, are complementary to those obtained from low-energy tau decays at BaBar and Belle, as well as projections from Belle-II.