Probing Lepton Flavor Violation at the ILC and CLIC

TL;DR

This paper investigates the potential of future electron-positron colliders, ILC and CLIC, to detect lepton flavor violation in the tau-muon sector using the SMEFT framework, highlighting their sensitivity to new physics.

Contribution

It demonstrates how beam polarization and high energy at ILC and CLIC can enhance sensitivity to lepton flavor violation, surpassing current tau decay constraints.

Findings

Beam polarization helps probe operator chirality.

High energy increases sensitivity to four-fermion operators.

Sensitivity can surpass Belle-II tau decay limits.

Abstract

Lepton flavor violation in the $\tau\mu$ sector would be a clear sign of Beyond Standard Model physics. We employ the SMEFT framework to study the process $e^+e^-\to\tau\mu$ at the ILC and CLIC. We find that the $e^+e^-$ beam polarizations achievable at these machines allow us to probe the chirality structure of the SMEFT operators. In addition, the high center of mass energy leads to a substantial increase in sensitivity to the four-fermion operators that rivals, and in some cases, surpasses tau decay projections from Belle-II.