Search for resonant and non-resonant Higgs boson pair production in the $b\bar b\tau^+\tau^-$ decay channel using 13 TeV $pp$ collision data from the ATLAS detector

TL;DR

This paper reports a search for Higgs boson pair production in the $b\bar{b}\tau^+\tau^-$ decay channel using 13 TeV proton-proton collision data from ATLAS, setting limits on production cross-sections and observing a local excess at 1 TeV.

Contribution

First search to analyze Higgs pair production in the $b\bar{b}\tau^+\tau^-$ channel with full Run 2 ATLAS data, providing new limits and a potential resonance signal.

Findings

No significant non-resonant excess observed.

A 3.1σ local excess at 1 TeV resonance mass.

Upper limits set on cross-sections for both resonant and non-resonant production.

Abstract

A search for Higgs boson pair production in events with two $b$-jets and two $\tau$-leptons is presented, using a proton-proton collision dataset with an integrated luminosity of 139 fb$^{-1}$ collected at $\sqrt{s}=13$ TeV by the ATLAS experiment at the LHC. Higgs boson pairs produced non-resonantly or in the decay of a narrow scalar resonance in the mass range from 251 to 1600 GeV are targeted. Events in which at least one $\tau$-lepton decays hadronically are considered, and multivariate discriminants are used to reject the backgrounds. No significant excess of events above the expected background is observed in the non-resonant search. The largest excess in the resonant search is observed at a resonance mass of 1 TeV, with a local (global) significance of $3.1\sigma$ ($2.0\sigma$). Observed (expected) 95% confidence-level upper limits are set on the non-resonant Higgs boson pair-production cross-section at 4.7 (3.9) times the Standard Model prediction, assuming Standard Model kinematics, and on the resonant Higgs boson pair-production cross-section at between 21 and 900 fb (12 and 840 fb), depending on the mass of the narrow scalar resonance.