Tau leptons can have lepton-flavor-violating (LFV) couplings to a muon or an electron and an Axion-Like Particle (ALP). ALPs are pseudo Nambu-Goldstone bosons associated with the spontaneously broken global $U(1)_{\mathrm{PQ}}$ symmetry. LFV ALPs have been of a great interest in the last several decades as they can solve some of the SM long-lasting problems. Assuming a future muon collider...
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+ → eτ process is revisited by means of an effective field theory approach. We provide constraints at 95% C.L. on the dimension-six...
