Probing electroweak phase transition in the singlet Standard Model via bbγγ and 4 l channels

bstract We investigate the prospects for resonant di-Higgs and heavy Higgs production searches at the 14 TeV HL-LHC in the combination of bbγγ and 4 l channels, as a probe of a possible first order electroweak phase transition in real singlet scalar extension of the Standard Model. Event selection follows those utilized in the bbγγ and 4 l searches by the ATLAS Collaboration, applied to simulation using benchmark parameters that realize a strong first order electroweak phase transition. The output of discriminant analysis is implemented by numerical calculation, optimised by the joint restriction from the two channels. The prospective reach for bbγγ /4 l channel could be more competitive in probing the electroweak phase transition at lower/higher resonance masses. With 3 ab − 1 integrated luminosity, the combination of the bbγγ and 4 l channels can discover/exclude a significant portion of the viable parameter space that realizes a strong first order phase transition when the resonance mass is heavier than 500 GeV.