New physics implications of VBF searches exemplified through the Georgi-Machacek model

TL;DR

This paper uses LHC VBF search data to constrain the Georgi-Machacek model, revealing how theoretical and experimental constraints guide the model towards the decoupling limit and impact electroweak symmetry breaking insights.

Contribution

It introduces a reparametrization of scalar potential couplings and demonstrates how combined constraints influence the Georgi-Machacek model's parameter space.

Findings

VBF searches effectively constrain nonstandard scalars in the GM model.

Theoretical and experimental constraints favor the decoupling limit.

VBF data provides insights into the electroweak vacuum composition.

Abstract

LHC searches for nonstandard scalars in vector boson fusion (VBF) production processes can be particularly efficient in probing scalars belonging to triplet or higher multiplet representations of the Standard Model $SU(2)_L$ gauge group. They can be especially relevant for models where the additional scalars do not have any tree-level couplings to the Standard Model fermions, rendering VBF as their primary production mode at the LHC. In this work, we employ the latest LHC data from VBF resonance searches to constrain the properties of nonstandard scalars, taking the Georgi-Machacek model as a prototypical example. We take into account the theoretical constraints on the potential from unitarity and boundedness-from-below as well as indirect constraints coming from the signal strength measurements of the 125 GeV Higgs boson at the LHC. To facilitate the phenomenological analysis we advocate a convenient reparametrization of the trilinear couplings in the scalar potential. We derive simple correlations among the model parameters corresponding to the decoupling limit of the model. We explicitly demonstrate how a combination of theoretical and phenomenological constraints can push the GM model towards the decoupling limit. Our analysis suggests that the VBF searches can provide key insights into the composition of the electroweak vacuum expectation value.