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

TL;DR

This paper analyzes a left-right symmetric extension of the Standard Model with doublet-induced symmetry breaking, showing it can accommodate diverse breaking patterns and constrains the symmetry breaking scale to a few TeV based on various experimental data.

Contribution

It introduces a doublet-based left-right symmetric model that preserves the electroweak ρ parameter and explores its phenomenological constraints, expanding beyond the commonly studied triplet models.

Findings

The symmetry breaking scale is constrained to a few TeV.

The model allows electroweak symmetry breaking via both bi-doublet and doublet.

Constraints from unitarity and electroweak precision data are compatible with the model.

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 $\rho$ 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 $\Delta r$ 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 \times SU(2)_R $ bi-doublet, which is the case most commonly considered in the literature, but also by the $ SU(2)_L $ doublet.