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 $f{b}^{-1}$. 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.