HEFT interpretations of Higgs boson pair searches in $b\bar{b} \gamma \gamma$ and $b\bar{b}\tau \tau$ final states and of their combination in ATLAS

This note presents interpretations of searches for Higgs boson pair ($HH$) production in the $b\bar{b}\gamma\gamma$ and $b\bar{b}\tau^+\tau^-$ final states, and of their combination, in terms of Higgs Effective Field Theory (HEFT) benchmark models. The searches make use of $139$ $\textrm{fb}^{-1}$ of proton-proton collision data recorded with the ATLAS detector at a centre-of-mass energy of $\sqrt{s}=13$ TeV at the LHC. Upper limits on the $HH$ production cross-section are set for seven HEFT benchmark models at $95$\% confidence level, with observed (expected) limits ranging from 50.4 (46.0) fb to 135.1 (135.1) fb. Exclusion limits are also set on two HEFT coupling parameters associated with the couplings of a Higgs boson pair with two gluons, $c_{gghh}$, and with a top-quark pair, $c_{tthh}$. Values of these parameters are excluded outside the observed (expected) ranges of $[-0.3 , 0.4 ]$ ($[-0.3, 0 .3]$) and $[-0.2, 0.6]$ ($[-0.2, 0.6]$), respectively, at the 95\% confidence level.