Prospects for the search for additional Higgs bosons in the ditau final state with the ATLAS detector at HL-LHC

Estimates of the sensitivity of the search for a heavy neutral Higgs boson in the $\tau\tau$ final state with the full High-Luminosity LHC dataset of 3000 $fb^{-1}$ proton-proton collisions at $\sqrt{s} =$ 14 TeV are presented. These estimates are based on the extrapolation of current results obtained with the 36.1 $fb^{-1}$ ATLAS dataset collected in 2015-2016 at $\sqrt{s} =$ 13 TeV. The expected 95 % CL upper exclusion limits or, in alternative, the expected 5 $\sigma$ discovery reach are presented in terms of cross section times branching fraction of the gluon fusion production and $b$-associated production. In the hypothesis that no signal emerges, results are interpreted in the context of MSSM benchmark scenarios, e.g. in the hMSSM scenario $\tan\beta>1$ is expected to be excluded for the mass range $250< m_A < 350$ GeV. The parameter space with the expected 5 $\sigma$ discovery reach is also shown. The impact of the systematic uncertainties is also discussed.