Status of negative coupling modifiers for extended Higgs sectors

TL;DR

This paper investigates the status of negative coupling modifiers in extended Higgs sectors, using experimental data to exclude such models and providing insights into custodial symmetry violation.

Contribution

It systematically analyzes weakly coupled extended Higgs models with larger multiplets, applying precision measurements to constrain negative coupling modifiers.

Findings

Negative $\lambda_{WZ}$ models are largely excluded by current data.

All minimal models with negative $\lambda_{WZ}$ are excluded at 95\\% confidence.

Evidence suggests negative $\lambda_{WZ}$ is unlikely in weakly coupled Higgs sectors.

Abstract

In this work, we study the status of negative coupling modifiers in extended Higgs sectors, focusing on the ratio of coupling modifiers that probes custodial symmetry violation $\lambda_{WZ} = \kappa_{W}/\kappa_{Z}$. Higgs sectors with multiplets larger than doublets are the only weakly coupled models that give tree-level modifications to $\lambda_{WZ}$, and we explore all such models allowed by the constraint from the $\rho$ parameter and perturbative unitarity. This class of models has a custodial symmetry violating potential, while the vacuum configuration preserves the symmetry. We apply precision measurements from ATLAS and CMS and show that each data set can exclude a vast set of models with $\lambda_{WZ} < 0$ at greater than 95\% confidence level. We give evidence that $\lambda_{WZ}<0$ is excluded in all weakly coupled models. [Erratum for this work on page 19 changing our claims of complete exclusion of negative $\lambda_{WZ}$ to a softer version where only the minimal models are excluded.]