Search for lepton-flavor violation in Z-boson decays with τ Leptons with the ATLAS detector

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM ; A search for lepton-flavor-violating Z → eꞇ and Z → μꞇ decays with pp collision data recorded by the ATLAS detector at the LHC is presented. This analysis uses 139 fb-1 of Run 2 pp collisions at √s = 13 TeV and is combined with the results of a similar ATLAS search in the final state in which the ꞇ lepton decays hadronically, using the same data set as well as Run 1 data. The addition of leptonically decaying ꞇ leptons significantly improves the sensitivity reach for Z → ℓꞇ decays. The Z → ℓ branching fractions are constrained in this analysis to B(Z → eꞇ) < 7.0 × 10-6 and B(Z → μꞇ) < 7.2 × 10-6 at 95% confidence level. The combination with the previously published analyses sets the strongest constraints to date: B(Z → eꞇ) < 5.0 × 10-6 and B(Z → μꞇ) < 6.5 × 10-6 at 95% confidence level