Cross-section measurements of boosted Higgs boson production in final states with pairs of hadronically decaying $\tau$-leptons with the ATLAS experiment

Abstract

Cross section measurements of high-Lorentz boosted Higgs boson production in final states with pairs of hadronically decaying $\tau$-leptons are presented. The analysis is based on the full Run 2 data sample of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of 140 ${\mathrm{fb}}^{-1}$, and a partial Run 3 data sample at $\sqrt{s}=13.6$ TeV with an integrated luminosity of 162 ${\mathrm{fb}}^{-1}$ collected in 2022-2024 with the ATLAS experiment. The analysis extends the sensitivity of previous $H\to \tau \tau$ measurements to Higgs boson transverse momenta above 300 GeV by reconstructing $\tau$-lepton pairs produced with a small separation in large radius jets. The standard reconstruction of hadronic $\tau$-leptons has limited efficiency in this phase space, requiring dedicated boosted di-$\tau$ reconstruction and identification techniques, combined with multivariate analysis methods, to extract the signal. For Higgs boson transverse momenta above 300 GeV, results are presented for both inclusive and differential cross-sections. Within the simplified template cross-section framework, differential cross-section measurements in Higgs boson transverse momentum for gluon-gluon fusion production are provided, together with an inclusive cross-section measurement for vector-boson fusion production. For the inclusive measurement, the analysis yields an observed (expected) significance of 3.8 (3.3) standard deviations over the background-only hypothesis, providing evidence of Higgs boson production in the boosted regime of the di-$\tau$ final state.

Comments: 55 pages in total, author list starting page 38, 12 figures, 8 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGP-2024-49