We investigate diboson signals in the standard model (SM) with an extended Higgs sector, motivated by the excesses in the diboson channels at the LHC. We begin with the unitarity sum rules of the weak gauge boson scattering assuming the Higgs sector is extended. According to the sum rules, we discuss the Higgs interpretations of the diboson signals and the consistency with the ATLAS diboson anomaly and other experimental constraints. As a concrete example, we propose a two-Higgs-doublet model where the Yukawa coupling of an extra $CP$-even scalar with up-type quark is relatively large. The diboson ($WW$ and $ZZ$) signals can be explained by 2 TeV $CP$-even Higgs boson, while the partners, the $CP$-odd and the charged Higgs bosons in the extra doublet, are severely constrained by both the LHC direct search and the indirect search via flavor observables. Especially, in order to avoid the diboson resonance search in the $Vh$ channel, further extensions of the model are required. The diboson excess is correlated with the SM Higgs signals in our framework, so that the precise measurement of the SM Higgs boson is also important to test the Higgs interpretation.

• Received 20 August 2015

DOI:https://doi.org/10.1103/PhysRevD.92.055015