Unitarity implications of a diboson resonance in the TeV region for Higgs physics

We investigate the implications of a putative new resonance in the TeV region coupled to the weak bosons. By studying perturbative unitarity of longitudinal $WW$ scattering, we find that a weakly coupled spin-1 resonance, that explains the ATLAS diboson excesses, is allowed with a SM-like Higgs. On the other hand, larger values of the resonance couplings, preferred in models of strong dynamics, would imply either sizeable reduction of the Higgs couplings or new physics, beyond the diboson resonance, at a few TeV.

Figure 1

Isoline ${\sigma }_{VV}=10\mathrm{fb}$ in the $g_q$–$g_{R\varphi \varphi }$ space (solid curve). The dark region in the lower right corner is excluded by ${\sigma }_{qq}<200\mathrm{fb}$ for $g_{\ell }=0$. The lighter shaded region is excluded by ${\sigma }_{\ell \ell }<0.5\mathrm{fb}$, assuming $g_q=g_l$. The dashed lines correspond to fixed values ${\mathrm{\Gamma }}_{\text{tot}}/M_R=10\%$ and 20%.

Figure 2

Contours of fixed scale where perturbative unitarity is lost, ${\mathrm{\Lambda }}_{\mathrm{NP}}=2$, 5 and 10 TeV, in the plane ${\delta }_h$ versus $g_{R\varphi \varphi }$. The region in white is where the cutoff is above 10 TeV. The horizontal lines mark the lower bounds on $g_{R\varphi \varphi }$ for a leptophobic $R$, and in the case of equal coupling to leptons and quarks.