Abstract
Charged Higgs bosons produced either in top-quark decays or in association with a top quark, subsequently decaying via H-+/- -> tau(+/-) nu(tau), are searched for in 140 fb(-1) of proton-proton collision data at root s = 13 TeV recorded with the ATLAS detector. Depending on whether the top quark is produced ffiffis together with the H-+/- decays hadronically or semileptonically, the search targets tau + jets or tau + lepton final states, in both cases with a tau-lepton decaying into a neutrino and hadrons. No significant excess over the Standard Model background expectation is observed. For the mass range of 80 <= m(H)(+/-) <= 3000 GeV, upper limits at 95% confidence level are set on the production cross section of the charged Higgs boson times the branching fraction B(H-+/- -> tau(+/-) nu(tau)) in the range 4.5 pb-0.4 fb. In the mass range 80-160 GeV, assuming the Standard Model cross section for tt production, this corresponds to upper limits between 0.27% and 0.02% on B(t -> bH(+/-)) x B(H-+/- ->tau(+/-) nu(tau)).