Resonant di-Higgs boson production in the b(b)over-barWW channel: Probing the electroweak phase transition at the LHC

We analyze the prospects for resonant di-Higgs production searches at the LHC in the b (b) over barW(+)W(-) (W+ -> l(+)nu(l), W- -> l(-)(nu) over bar (l)) channel, as a probe of the nature of the electroweak phase transition in Higgs portal extensions of the Standard Model. In order to maximize the sensitivity in this final state, we develop a new algorithm for the reconstruction of the b (b) over barW(+)W(-) invariant mass in the presence of neutrinos from the W decays, building from a technique developed for the reconstruction of resonances decaying to tau(+) tau(-) pairs. We show that resonant di-Higgs production in the b (b) over barW(+)W(-) channel could be a competitive probe of the electroweak phase transition already with the data sets to be collected by the CMS and ATLAS experiments in run 2 of the LHC. The increase in sensitivity with larger amounts of data accumulated during the high-luminosity LHC phase can be sufficient to enable a potential discovery of the resonant di-Higgs production in this channel.