Speaker
Description
This report presents a combination of searches for Higgs boson pairs using up to 36.1 fb$^{−1}$ of proton-proton collision data at a centre-of-mass energy $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the LHC. The combination is performed using three analyses searching for the $HH\rightarrow b\bar{b}b\bar{b}$, $HH\rightarrow b\bar{b}\tau^{+}\tau^{-}$ and $HH\rightarrow b\bar{b}\gamma\gamma$ decay channels. Results are presented for both non-resonant and resonant Higgs boson pair production modes. The combined observed (expected) limit on the non-resonant Higgs boson pair cross-section is 0.22 pb (0.35 pb) at 95% confidence level, which corresponds to 6.7 (10.4) times the predicted Standard Model cross-section. The ratio of the Higgs boson self-coupling to its Standard Model expectation $(\kappa_{\lambda}=\lambda_{HHH}/\lambda_{HHH}^{\mathrm{SM}})$ is observed (expected) to be constrained at 95% confidence level to $-5.0<\kappa_{\lambda}<12.1$ ($-5.8<\kappa_{\lambda}<12.0$). Exclusion limits are also set on resonant Higgs boson pair production, probing a model with an extended Higgs sector based on two doublets, as well as a Randall-Sundrum bulk graviton model.
