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

Constraints on the Higgs boson self-coupling are set by combining double-Higgs boson analyses bb̄bb̄,bb̄τ + τ − and bb̄γγ decay channels The data used in these analyses were recorded by the ATLAS detector at the √ LHC in proton–proton collisions at s = 13 TeV and correspond to an integrated luminosity of 126–139 f b −1 . The combination of the double- Higgs analyses sets an upper limit of µ HH < 2.4 at 95% confidence level on the double-Higgs production and constraints for κ λ between -0.6 and 6.6. The obtained boundaries for κ 2V coupling modifier are [0.1:2.0] . The HL-LHC prospects have been also considered and the expected limit with 3000 f b −1 collected data is 0.55 for signal strength and κ λ between 0.0 and 2.5 for the baseline scenario.