A low-energy perspective on the minimal left-right symmetric model

W Dekens,J De Vries,L Andreoli,F Oosterhof,E Mereghetti

doi:10.1007/jhep11(2021)127

Abstract

We perform a global analysis of the low-energy phenomenology of the minimal left-right symmetric model (mLRSM) with parity symmetry. We match the mLRSM to the Standard Model Effective Field Theory Lagrangian at the left-right-symmetry breaking scale and perform a comprehensive fit to low-energy data including mesonic, neutron, and nuclear β-decay processes, ∆F = 1 and ∆F = 2 CP-even and -odd processes in the bottom and strange sectors, and electric dipole moments (EDMs) of nucleons, nuclei, and atoms. We fit the Cabibbo-Kobayashi-Maskawa and mLRSM parameters simultaneously and determine a lower bound on the mass of the right-handed WR boson. In models where a Peccei-Quinn mechanism provides a solution to the strong CP problem, we obtain {M}_{W_R} ≳ 5.5 TeV at 95% C.L. which can be significantly improved with next-generation EDM experiments. In the P-symmetric mLRSM without a Peccei-Quinn mechanism we obtain a more stringent constraint {M}_{W_R} ≳ 17 TeV at 95% C.L., which is difficult to improve with low-energy measurements alone. In all cases, the additional scalar fields of the mLRSM are required to be a few times heavier than the right-handed gauge bosons. We consider a recent discrepancy in tests of first-row unitarity of the CKM matrix. We find that, while TeV-scale WR bosons can alleviate some of the tension found in the Vud,us determinations, a solution to the discrepancy is disfavored when taking into account other low-energy observables within the mLRSM.

Highlights

Left-right (LR) symmetric models [2,3,4,5,6] provide a framework for a dynamical theory of parity (P ) violation and led to the prediction of right-handed neutrinos and the see-saw mechanism, well before neutrino oscillations were discovered [7, 8]
The presence of right-handed charged currents mediated by WR exchange and of heavy scalar bosons with flavor-changing interactions lead to a rich flavor phenomenology, with new contributions to a broad range of processes including CP violation in meson mixing and decays [16,17,18,19,20,21,22], nuclear β-decay [23, 24], electroweak precision observables [25,26,27], and electric dipole moments (EDMs) of leptons, nucleons, nuclei, atoms, and molecules [28,29,30,31]
We focus on the version of the LR model, called the minimal left-right symmetric model, in which this is done with two triplets, ∆L,R, assigned to (3, 1, 2) and (1, 3, 2), respectively

Summary

Introduction

Left-right (LR) symmetric models [2,3,4,5,6] provide a framework for a dynamical theory of parity (P ) violation and led to the prediction of right-handed neutrinos and the see-saw mechanism, well before neutrino oscillations were discovered [7, 8]. Apart from providing a natural explanation of parity violation and neutrino masses, LR models give rise to a rich phenomenology. The presence of right-handed charged currents mediated by WR exchange and of heavy scalar bosons with flavor-changing interactions lead to a rich flavor phenomenology, with new contributions to a broad range of processes including CP violation in meson mixing and decays [16,17,18,19,20,21,22], nuclear β-decay [23, 24], electroweak precision observables [25,26,27], and electric dipole moments (EDMs) of leptons, nucleons, nuclei, atoms, and molecules [28,29,30,31]

Objectives

Results

Conclusion