Measurement of the VH,H → ττ process with the ATLAS detector at 13 TeV

A measurement of the Standard Model Higgs boson produced in association with a W or Z boson and decaying into a pair of τ-leptons is presented. This search is based on proton-proton collision data collected at √s = 13 TeV by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 140 fb⁻¹. For the Higgs boson candidate, only final states with at least one τ-lepton decaying hadronically (τ → hadrons + ν_t) are considered. For the vector bosons, only leptonic decay channels are considered: Z → ll and W → lν _l and with l = e, μ. An excess of events over the expected background is found with an observed (expected) significance of 4.2 (3.6) standard deviations, providing evidence of the Higgs boson produced in association with a vector boson and decaying into a pair of τ-leptons. The ratio of the measured cross-section to the Standard Model prediction is μ^ττ_VH  = 1.28+^0.30_-0.29 (stat.) +^0.25_-0.21 (syst.). This result represents the most accurate measurement of the VH(ττ) process achieved to date.