Why PeV scale left–right symmetry is a good thing

Abstract

Left-right symmetric gauge theory presents a minimal paradigm to accommodate massive neutrinos with all known conserved symmetries duly gauged. The work presented here is based on the argument that the see-saw mechanism does not force the new right handed symmetry scale to be very high, and as such some of the species from the spectrum of the new gauge and Higgs bosons can have masses within a few orders of magnitude of the TeV scale. The scale of the left-right parity breaking in turn can be sequestered from the Planck scale by supersymmetry. We have studied several formulations of such Just Beyond Standard Model (JBSM) theories for their consistency with cosmology. Specifically the need to eliminate phenomenologically undesirable domain walls gives many useful clues. The possibility that the exact left-right symmetry breaks in conjunction with supersymmetry has been explored in the context of gauge mediation, placing restrictions on the available parameter space. Finally we have also studied a left-right symmetric model in the context of metastable supersymmetric vacua and obtained constraints on the mass scale of Right handed symmetry. In all the cases studied, The mass scale of right handed neutrino $M_R$ remains bounded from above, and in some of the cases the scale $10^9$ GeV favourable for supersymmetric thermal leptogenesis is disallowed. On the other hand PeV scale remains a viable option, and the results warrant a more detailed study of such models for their observability in collider and astroparticle experiments.