Projection of $H\to\tau\tau$ cross-section measurement results to the HL-LHC

An extrapolation to assess the expected sensitivity of ${pp \rightarrow H\rightarrow \tau\tau}$ cross-section measurements at the HL-LHC is performed using the results obtained with $139 \ \mathrm{fb}^{-1}$ of $pp\ $ collisions at $\sqrt{s} = 13$ TeV. A HL-LHC scenario corresponding to a dataset of $3000 \ \mathrm{fb}^{-1}$ of $pp$ collisions at $\sqrt{s} = 14$ TeV is considered. The results consist of the measurements of the total ${pp \rightarrow H\rightarrow \tau\tau}$ cross-section as well as of the four main Higgs boson production cross-sections (gluon-gluon fusion, vector-boson fusion, associated production with a vector boson and associated production with a top quark pair). A study of their kinematic dependence is also presented within the Simplified Template Cross-Section (STXS) framework. The obtained results indicate that a total uncertainty of 5% on the ${pp \rightarrow H\rightarrow \tau\tau}$ cross-section measurement could be achieved at the HL-LHC. For the four main production modes, the uncertainties are expected to be of 11% for gluon-gluon fusion, 7% for vector-boson fusion, 14% for associated production with a vector boson and 24% for associated production with a top quark pair. The precision of the cross-section measurements within the STXS framework ranges from 7% to 50% depending on the bin, with the smallest uncertainties corresponding to STXS bins sensitive to events within vector-boson fusion topologies, and gluon-gluon fusion events where the Higgs boson has a high transverse momentum.