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

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

“…The high-energy analogue, the so-called Keung-Senjanović process [15], is a promising probe of the same source of lepton number violation at the LHC or future colliders. In addition, the presence of right-handed charged currents mediated by W R 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].…”

“…These relations assume that the 27L,R × 1R,L parts of the LL and RR operators provide negligible contributions to the (ππ)I=0|Oi|K 0 matrix elements. These contributions can be obtained by using the LEC of the 27L,R × 1R,L representations, A(27,1) , discussed in section 5.2. Such an estimate shows that the dominant contributions to M1,2 indeed arise from the 8L,R × 1R,L parts of the operators.…”

Observing Left-Right Symmetry in the Cosmic Microwave Background

“…Conventionally, the very first proposals and studies of LRSM [1][2][3][4][5] considered a scalar bidoublet for generating fermion masses and also for electroweak symmetry breaking whereas a pair of scalar doublets were introduced for the purpose of left-right symmetry breaking at high energy scale. A very recent detailed study of this model can be found in [22]. On the other hand, the LRSM proposals put forward later [7][8][9][10][11][12] received much more attention due to the possibility of seesaw origin of light neutrino masses through a combination of type I seesaw [23][24][25][26] and type II seesaw [8,[27][28][29][30] or type III seesaw [31].…”

“…The gauge structure of the model prevents any renormalisable Yukawa couplings involving the scalar doublets χ L,R . The scalar potential V scalar is given by [22] V…”

“…For details of the minimisation of the scalar potential and resulting symmetry breaking, please refer to [22]. In the symmetry breaking pattern, the neutral component of the Higgs doublet χ R acquires a vacuum expectation value (VEV) to break the gauge symmetry of the DLRM into that of the SM and then to the U (1) of electromagnetism by the VEV of the neutral components of Higgs bidoublet Φ:…”