Fermion Masses in Emergent Electroweak Symmetry Breaking

TL;DR

This paper proposes a model where electroweak symmetry breaking and fermion masses emerge from strong dynamics without a fundamental Higgs, predicting measurable deviations in top quark couplings.

Contribution

It introduces a warped extra dimension model with composite gauge bosons and boundary mass terms, providing a novel mechanism for fermion mass generation without a Higgs.

Findings

Top quark couplings can deviate by 10-20% from Standard Model predictions.

Electroweak symmetry is emergent, not fundamental, arising from confining strong dynamics.

Flavor-dependent nonuniversality affects gauge couplings, especially for the top quark.

Abstract

We consider the generation of fermion masses in an emergent model of electroweak symmetry breaking with composite $W,Z$ gauge bosons. A universal bulk fermion profile in a warped extra dimension is used for all fermion flavors. Electroweak symmetry is broken at the UV (or Planck) scale where boundary mass terms are added to generate the fermion flavor structure. This leads to flavor-dependent nonuniversality in the gauge couplings. The effects are suppressed for the light fermion generations but are enhanced for the top quark where the $Zt{\bar t}$ and $Wt{\bar b}$ couplings can deviate at the $10-20%$ level in the minimal setup. By the AdS/CFT correspondence our model implies that electroweak symmetry is not a fundamental gauge symmetry. Instead the Standard Model with massive fermions and $W,Z$ gauge bosons is an effective chiral Lagrangian for some underlying confining strong dynamics at the TeV scale, where mass is generated without a Higgs mechanism.