Searching for lepton flavor violating interactions at future electron-positron colliders

TL;DR

This study assesses the potential of future electron-positron colliders to detect lepton flavor violating interactions using an effective field theory approach, providing projected constraints on new physics couplings at various energies.

Contribution

It offers the first detailed sensitivity analysis of future colliders for lepton flavor violation via four-fermion interactions, incorporating realistic detector effects and background considerations.

Findings

Significant improvement in sensitivity when combining results from multiple energies.

Projected constraints on Wilson coefficients at 95% CL for future colliders.

Comparison showing future colliders' potential surpasses current experiments like Belle II.

Abstract

Lepton flavor violating interactions are absent in the standard model but are expected in various beyond standard models. In this work, the potential of the future circular electron-positron collider to probe the four fermion lepton flavor couplings via the $e^{+}e^{-}\rightarrow e^{\pm}\tau^{\mp}$ process is revisited by means of an effective field theory approach. We provide constraints at $95\%$ CL on the dimension-six Wilson coefficients including major sources of background processes and considering realistic detector effects at four expected operation energies $\sqrt{s}=157.5$, $162.5$, $240$ and $365$ GeV according to their corresponding integrated luminosities. We demonstrate that statistical combination of the results from four center-of-mass energies improves the sensitivity to the LFV couplings significantly. We compare the results with the prospects from Belle II with $50~ ab^{-1}$ and other studies at electron-positron colliders.