Heavy Higgs boson coupled to vectorlike quarks: StrongCPproblem and search prospects at the 14 TeV LHC

Motivated by a solution to the strong $CP$ problem, we propose a model where a new heavy neutral $CP$-even Higgs boson couples to vectorlike quarks enhancing its production cross section whose dominant decays are into weak bosons. The masses of the vectorlike quarks are generated through interactions with a singlet scalar field charged under a broken global $U(1)$ symmetry, providing a solution to the strong $CP$ problem by means of the Peccei-Quinn mechanism. The diboson excess observed by the ATLAS Collaboration is discussed as the new heavy Higgs boson is a candidate to explain a possible signal in this channel. We also show that the 14 TeV LHC is capable of discovering this heavy Higgs with masses up to 1 TeV in the $H\ensuremath{\rightarrow}ZZ\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{\ensuremath{'}+}{\ensuremath{\ell}}^{\ensuremath{'}\ensuremath{-}}$ search channel using boosted decision trees to better discriminate between signals and backgrounds and to tame systematic uncertainties in the background rates.