Discovering heavy U(1)-gauged Higgs bosons at the HL-LHC

We determine the discovery potential of the Large Hadron Collider (LHC) at 13 TeV center-of-mass energy for a heavy scalar resonance in the dilepton channel. In particular, we consider the singlet-like heavy mass eigenstate of a mixed two Higgs doublet and scalar singlet model in the U(1)_B−L extension of the standard model. We find that, despite the small coupling of the singlet scalar with the doublets, this heavy scalar can be discovered with 5σ at the LHC with integrated luminosities of ∼300 to 1400 fb⁻¹ in the mass range between 500 GeV and 1 TeV. (paper)