Extracting the mass scale of a second Higgs boson from a deviation in $h(125)$ couplings

TL;DR

This paper explores how deviations in the Higgs boson $h(125)$ couplings can be used to estimate the mass scale of a potential second Higgs boson within non-minimal Higgs models, combining theoretical and experimental constraints.

Contribution

It provides a comprehensive analysis linking Higgs coupling deviations to the upper bounds on the second Higgs boson mass in models satisfying electroweak precision constraints.

Findings

Derived an upper limit on the second Higgs mass based on theoretical and experimental bounds.

Identified the relationship between $h(125)$ coupling deviations and the second Higgs mass.

Discussed the complementarity of direct and indirect search constraints.

Abstract

We investigate the correlation between a possible deviation in the discovered Higgs boson $h(125)$ couplings from the Standard Model prediction and the mass scale ($M_{\text{2nd}}$) of the next-to-lightest Higgs boson in models with non-minimal Higgs sectors. In particular, we comprehensively study a class of next-to-minimal Higgs sectors which satisfy the electroweak $\rho$ parameter to be one at tree level. We derive an upper limit on $M_{\text{2nd}}$ by imposing bounds from perturbative unitarity, vacuum stability, triviality and electroweak precision data as functions of the deviation in the $hVV$ ($V=W,Z$) couplings. Furthermore, we discuss the complementarity between these bounds and the current LHC data, e.g., by considering direct searches for additional Higgs bosons and indirect constraints arising from the measured $h(125)$ signal strengths.