Searching for Neutral BSM Higgs Bosons in the $\tau\tau$ Decay Channel Using Full Run-2 Data from the ATLAS Detector

A search for heavy neutral Higgs bosons is performed using the LHC Run 2 data, corresponding to an integrated luminosity of 139 fb$^{−1}$ of proton–proton collisions at $\sqrt{s} = 13$ TeV recorded with the ATLAS detector. The heavy resonance is searched for in the $\tau^+\tau^-$ decay mode with at least one $\tau$ lepton decaying into final states with hadrons and a neutrino. The search covers the mass range of 0.2–2.5 TeV. The data are in good agreement with the background predicted by the Standard Model. In the context of the $M_h^{125}$ scenario of the Minimal Supersymmetric Standard Model, the data exclude $\tan\beta > 21$ for $m_A = 1.5$ TeV at the 95% confidence level.