Extended scalar sectors, effective operators and observed data

TL;DR

This paper analyzes 125 GeV Higgs data to constrain new physics in extended scalar sectors using model-independent effective operators and applies these constraints to specific two Higgs doublet and scalar triplet models.

Contribution

It introduces a combined approach of model-independent effective operators and model-specific fits to constrain extended scalar sector parameters using observed Higgs data.

Findings

Constraints on effective operator coefficients from Higgs data

Allowed parameter regions for two Higgs doublet models

Limits on scalar triplet models based on observed data

Abstract

The available data on the 125 GeV scalar $h$ is analysed to explore the room for new physics in the electroweak symmetry breaking sector. The first part of the study is model-independent, with $h$ couplings to standard model particles scaled by quantities that are taken to be free parameters. At the same time, the additional loop contributions to $h \rightarrow \gamma\gamma$ and $h \rightarrow Z\gamma$, mediated by charged scalar contributions in the extended scalar sector, are treated in terms of gauge-invariant effective operators. Having justified this approach for cases where the concerned scalar masses are a little above the $Z$-boson mass, we fit the existing data to obtain marginalized 1$\sigma$ and 2$\sigma$ regions in the space of the coefficients of such effective operators, where the limit on the $h \rightarrow Z\gamma$ branching ratio is used as a constraint. The correlation between, say, the gluon fusion and vector-boson fusion channels, as reflected in a non-diagonal covariance matrix, is taken into account. After thus obtaining model-independent fits, the allowed values of the coefficients are translated into permissible regions of the parameter spaces of several specific models. In this spirit we constrain four different types of two Higgs doublet models, and also models with one or two $Y = 2$ scalar triplets, taking into account the correlatedness of the scale factors in $h$-interactions and the various couplings of charged Higgs states in each extended scenario.