Measurement of the $VH,H\to \tau \tau$ process with the ATLAS detector at 13 TeV

Abstract

A measurement of the Standard Model Higgs boson produced in association with a $W$ or $Z$ boson and decaying into a pair of $\tau$-leptons is presented. This search is based on proton-proton collision data collected at $\sqrt{s}=13$ 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 $\tau$-lepton decaying hadronically ($\tau \to \mathrm{hadrons}+{\nu }_{\tau }$) are considered. For the vector bosons, only leptonic decay channels are considered: $Z\to \ell \ell$ and $W\to \ell {\nu }_{\ell }$, with $\ell =e,\mu$. 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 $\tau$-leptons. The ratio of the measured cross-section to the Standard Model prediction is ${\mu }_{\text{VH}}^{\tau \tau }=1.28{}_{-0.29}^{+0.30}(stat.){}_{-0.21}^{+0.25}(syst.)$. This result represents the most accurate measurement of the \vh process achieved to date.

46 pages in total, author list starting on page 30, 5 figures, 6 tables. B. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2018-20/

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