Searches for lepton-flavour-violating decays of the Higgs boson in √s = 13 TeV pp collisions with the ATLAS detector

This Letter presents direct searches for lepton flavour violation in Higgs boson decays, H -> eτ  and H -> μτ, performed with the ATLAS detector at the LHC. The searches are based on a data sample of proton–proton collisions at a centre-of-mass energy √s = 13 TeV, corresponding to an integrated luminosity of 36.1 fb^-1. No significant excess is observed above the expected background from Standard Model processes. The observed (median expected) 95% confidence-level upper limits on the lepton-flavour-violating branching ratios are 0.47% (0.34^+0.13_-0.10%) and 0.28% (0.37^+0.14_-0.10%) for H -> eτ  and H -> μτ, respectively.