Speaker
Description
We consider a classically conformal $U(1)$ extension of the Standard Model (SM). The $U(1)$ symmetry is radiatively broken by the Coleman-Weinberg mechanism, after which the $U(1)$ Higgs field $\phi$ drives electroweak symmetry breaking through a mixed quartic coupling with the SM Higgs doublet with coupling constant $\lambda_{mix}$. We calculate the Higgs triple couplings in this system and find a suppression of the coupling $g_{h \phi \phi}$ when compared to the naively expected value $g_{h \phi \phi} \sim \lambda_{mix} v_{h}$ ($v_{h} = 246$ GeV), likely due to the unique nature of the classically conformal potential. The suppression opens up parameter space for the mixing angle $\theta$ between SM Higgs and $U(1)$ Higgs eigenstates. We consider experimental signals for such conformal structure via the anomalous Higgs decay $h \rightarrow \phi \phi$ and anomalous SM Higgs couplings. The conformal structure would allow for a sizeable anomalous SM Higgs coupling alongside a heavily suppressed $h \rightarrow \phi \phi$ decay mode.
