Still No Experimental Evidence Of Charged Lepton LFV

Experimental evidence continues to confirm that Standard Model rule that lepton flavor violation does not occur in the charged lepton sector (e.g. a Z boson cannot decay to an electron and an anti-muon, which would not conserve lepton flavor number, even though this decay would conserve total lepton number).

According to the ATLAS experiment at the LHC, the maximum branching fraction of lepton flavor violating decays from Z bosons is experimentally bounded to be not more than 7.5*10^-7 out of a total combined branching fraction of all possible decays of 1, compared to probabilities on the order of 3.363*10^-2 of the least common decays into a pair of Standard Model fundamental particles.  This bound is about 2.5 times stronger than the one currently listed by the Particle Data Group.

Of course, neutrinos oscillate, which is fundamentally a lepton flavor violating process. But, neutrino oscillation according to the PMNS matrix does not give rise indirectly to experimentally discernible lepton flavor violation in the charged lepton sector in the Standard Model.