Constraining the gauge and scalar sectors of the doublet left-right symmetric model

Véronique Bernard,Luiz Vale Silva,Sébastien Descotes-Genon

doi:10.1007/jhep09(2020)088

Abstract

We consider a left-right symmetric extension of the Standard Model where the spontaneous breakdown of the left-right symmetry is triggered by doublets. The electroweak ρ parameter is protected from large corrections in this Doublet Left-Right Model (DLRM), contrary to the triplet case. This allows in principle for more diverse patterns of symmetry breaking. We consider several constraints on the gauge and scalar sectors of DLRM: the unitarity of scattering processes involving gauge bosons with longitudinal polarisations, the radiative corrections to the muon ∆r parameter and the electroweak precision observables measured at the Z pole and at low energies. Combining these constraints within the frequentist CKMfitter approach, we see that the fit pushes the scale of left-right symmetry breaking up to a few TeV, while favouring an electroweak symmetry breaking triggered not only by the SU(2)L×SU(2)R bi-doublet, which is the case most commonly considered in the literature, but also by the SU(2)L doublet.

Highlights

Left-Right (LR) symmetric models constitute a category of extensions of the SM that explains the left-handed structure of the SM through the existence of a larger gauge group SU (3)C ⊗SU (2)L×SU (2)R×U (1)X
This allows in principle for more diverse patterns of symmetry breaking
We have considered a left-right symmetric extension of the Standard Model where the spontaneous breakdown of the left-right symmetry is triggered by doublets

Summary

Introduction

Left-Right (LR) symmetric models constitute a category of extensions of the SM that explains the left-handed structure of the SM through the existence of a larger gauge group SU (3)C ⊗SU (2)L×SU (2)R×U (1)X. This group is broken first at a high-energy scale μR (of the order of the TeV or higher), inducing a difference between left and right sectors, followed by an electroweak symmetry breaking occurring at a lower scale μW [1,2,3,4,5]. Recent studies of anomalies in rare b-decays suggest the interest of having right-handed currents in order to provide a consistent explanation of all the measurements [10,11,12,13,14]

Methods

Results

Conclusion