Probing the nature of electroweak symmetry breaking with Higgs boson pairs in ATLAS

Constraints on the Higgs boson trilinear self-coupling modifier $\kappa_{\lambda}$ and non-SM HHVV coupling strength $\kappa_{2V}$ are set by combining di-Higgs boson analyses using $b\bar{b}b\bar{b}$, $b\bar{b}\tau^{+}\tau^{-}$ and $b\bar{b}\gamma\gamma$ decay channels. The data used in these analyses were recorded by the ATLAS detector at the Large Hadron Collider in proton-proton collisions at $\sqrt{s}$ = 13 TeV and corresponding to an integrated luminosity of 126-139 $fb^{-1}$. The combination of the di-Higgs analyses sets an upper limit of signal strength $\mu_{HH} <$ 2.4 at 95\% confidence level on the di-Higgs production and constraints for $\kappa_{\lambda}$ between -0.6 and 6.6. The obtained confidence interval for $\kappa_{2V}$ coupling modifier are [0.1,2.0]. The High Luminosity Large Hadron Collider prospects have been considered as well. The expected signal strength is 0.55 and $\kappa_{\lambda}$ between 0.0 and 2.5 for the baseline scenario.