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

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 electronpositron collider to probe the four fermion lepton flavor couplings via the e + e − → e ± τ ∓ 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 √ 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, improve 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.