Dynamical Symmetry Breaking With a Fourth Generation

TL;DR

This paper proposes that adding a fourth generation to the Standard Model can induce electroweak symmetry breaking through radiative corrections, predicting a Higgs mass of a few hundred GeV and a low cutoff scale around 1-2 TeV, with implications for LHC physics.

Contribution

It introduces a model where a fourth generation causes dynamical electroweak symmetry breaking via radiative effects, with detailed analysis of Higgs mass and cutoff scale.

Findings

Higgs mass predicted to be a few hundred GeV

Cutoff scale around 1-2 TeV compatible with data

New physics effects should be observable at the LHC

Abstract

Adding a fourth generation to the Standard Model and assuming it to be valid up to some cutoff \Lambda, we show that electroweak symmetry is broken by radiative corrections due to the fourth generation. The effects of the fourth generation are isolated using a Lagrangian with a genuine scalar without self-interactions at the classical level. For masses of the fourth generation consistent with electroweak precision data (including the B \rightarrow K \pi\ CP asymmetries) we obtain a Higgs mass of the order of a few hundreds GeV and a cutoff \Lambda\ around 1-2 TeV. We study the reliability of the perturbative treatment used to obtain these results taking into account the running of the Yukawa couplings of the fourth quark generation with the aid of the Renormalization Group (RG) equations, finding similar allowed values for the Higgs mass but a slightly lower cut-off due to the breaking of the perturbative regime. Such low cut-off means that the effects of new physics needed to describe electroweak interactions at energy above \Lambda\ should be measurable at the LHC. We use the minimal supersymmetric extension of the standard model with four generations as an explicit example of models realizing the dynamical electroweak symmetry breaking by radiative corrections and containing new physics. Here, the cutoff is replaced by the masses of the squarks and electroweak symmetry breaking by radiative corrections requires the squark masses to be of the order of 1 TeV.