Connecting Electroweak Symmetry Breaking and Flavor: A Light Dilaton ${\cal D}$ and a Sequential Heavy Quark Doublet $Q$

TL;DR

This paper explores the possibility that the 125 GeV boson is a dilaton related to electroweak symmetry breaking, proposing a dynamical mass generation mechanism involving a heavy quark doublet and discussing experimental implications.

Contribution

It introduces a model linking a light dilaton to dynamical mass generation via a heavy quark doublet with ultra-strong Yukawa coupling, connecting EWSB to flavor physics.

Findings

The 125 GeV boson could be a dilaton from scale invariance violation.

A heavy quark doublet with 4-5 TeV mass explains the absence of new physics signals.

Current LHC data shows correlations but also challenges from $t\bar tH$ production.

Abstract

The 125 GeV boson is quite consistent with the Higgs boson of the Standard Model (SM), but there is a challenge from Anderson whether this particle is in the Lagrangian. As LHC Run 2 takes its final year of running, we ought to reflect and make sure we have gotten everything right. The ATLAS and CMS combined Run 1 analysis claims 5.4$\sigma$ measurement of vector boson fusion (VBF) production that is consistent with SM, which seemingly refutes Anderson. However, to verify the source of electroweak symmetry breaking (EWSB), we caution that VBF measurement is too important for us to be imprudent in any way, and gluon-gluon fusion (ggF) with similar tag jets must be simultaneously \emph{measured}, which should be achievable at LHC Run 2. The point is to truly test the dilaton possibility, the pseudo-Goldstone boson of scale invariance violation. We illustrate EWSB by dynamical mass generation of a sequential quark doublet $Q$ via its ultrastrong Yukawa coupling, and argue how this might be consistent with a 125 GeV dilaton, ${\cal D}$. The ultraheavy $2m_Q \gtrsim 4$--5 TeV scale explains the absence of New Physics so far, while the mass generation mechanism shields us from the UV theory for the strong Yukawa coupling. Collider and flavor physics implications are briefly touched upon. Current Run 2 analyses show correlations between the ggF and VBF measurements, but the newly observed $t\bar tH$ production at LHC poses a challenge.