A Review of the Exceptional Supersymmetric Standard Model

Stephen F King,Stefano Moretti,Roman Nevzorov

doi:10.3390/sym12040557

Abstract

Local supersymmetry (SUSY) provides an attractive framework for the incorporation of gravity and unification of gauge interactions within Grand Unified Theories (GUTs). Its breakdown can lead to a variety of models with softly broken SUSY at low energies. In this review article, we focus on the SUSY extension of the Standard Model (SM) with an extra U ( 1 ) N gauge symmetry originating from a string-inspired E 6 GUTs. Only in this U ( 1 ) extension of the minimal supersymmetric standard model (MSSM) can the right-handed neutrinos be superheavy, providing a mechanism for the baryon asymmetry generation. The particle content of this exceptional supersymmetric standard model (E 6 SSM) includes three 27 representations of the E 6 group, to ensure anomaly cancellation. In addition it also contains a pair of S U ( 2 ) W doublets as required for the unification of gauge couplings. Thus, E 6 SSM involves exotic matter beyond the MSSM. We consider symmetries that permit suppressing flavor changing processes and rapid proton decay, as well as gauge coupling unification, the gauge symmetry breaking and the spectrum of Higgs bosons in this model. The possible Large Hadron Collider (LHC) signatures caused by the presence of exotic states are also discussed.

Highlights

Symmetries play a key role in modern high energy physics
When m3/2 MP, the breakdown of the E6 gauge group near the Grand Unified Theories (GUTs) scale MX can result in a variety of SUSY models at low energies including minimal supersymmetric standard model (MSSM) and its extensions with an extra U (1)0 gauge symmetry, which is a linear combination of U (1)χ and U (1)ψ, i.e., U (1)0 = U (1)χ cos θ E6 + U (1)ψ sin θ E6
The breakdown of an extended gauge symmetry in the string-inspired E6 GUTs may result in a variety of extensions of the standard model (SM) with softly broken SUSY at low energies including MSSM, NMSSM, U (1) extensions of the MSSM, etc

Summary

Introduction

Symmetries play a key role in modern high energy physics. it was realized a long time ago that light hadron resonances form representations of the SU (3) group, which is associated with light quark flavors, while the physics of strong interactions is described by the colored SU (3)C gauge symmetry. When m3/2 MP , the breakdown of the E6 gauge group near the GUT scale MX can result in a variety of SUSY models at low energies including MSSM and its extensions with an extra U (1)0 gauge symmetry, which is a linear combination of U (1)χ and U (1)ψ , i.e.,. The couplings of all other exotic states to the ordinary quark and lepton supermultiplets are forbidden that eliminates any problems related with the non-diagonal flavor transitions at the tree level In this original E6 SSM model, the scalar components of the supermultiplets. If some of the couplings λ, λαβ or κij are rather large at the GUT scale MX , they can lead to negative values of m2S at low energies This triggers the breakdown of U (1) N gauge symmetry giving rise to the large VEV of the singlet superfield S that generate sufficiently large masses of the exotic particles and Z 0 boson.

Gauge Coupling Unification

Gauge Symmetry Breaking and Higgs Sector

Higgs Spectrum

LHC Signatures

Conclusions