Impacts of multi-Higgs on the $\rho$ parameter, decays of a neutral Higgs to $WW$ and $ZZ$, and a charged Higgs to $WZ$

Abstract

In the standard model (SM), the $\rho$ parameter is equal to 1 and the ratio $\lambda_{WZ}$ of Higgs $\to ZZ$ and Higgs $\to WW$ is also equal to 1 at the tree level. When going beyond the SM with more than one types of Higgs representations these quantities may be different from the SM predictions which can provide crucial information about new physics. There may also exist a certain charged Higgs $h^+$ decays into a $W^+$ and a $Z$. Imposing a custodial symmetry can force the parameter $\rho$ to be equal to 1 with certain predictions for $\lambda_{WZ}$ and $h^+ \to W^+Z$. However, imposing $\rho =1$ without custodial symmetry may have different predictions. We show how differences arise and how to use experimental data to obtain information about the underlying physics in a model with the SM plus a real and a complex $SU(2)_L$ triplets.