Neutrinoless double beta decay in minimal left-right symmetric model with universal seesaw (1706.02456v2)

Abstract: We present a detailed discussion on neutrinoless double beta decay $(0\nu \beta \beta)$ within left-right symmetric models based on the gauge symmetry of type $SU(2)L \times SU(2)_R \times U(1){B-L}$ as well as $SU(3)L \times SU(3)_R \times U(1){X}$ where fermion masses including that of neutrinos are generated through a universal seesaw mechanism. We find that one or more of the right-handed neutrinos could be as light as a few keV if left-right symmetry breaking occurs in the range of a few TeV to 100 TeV. With such light right-handed neutrinos, we perform a detailed study of new physics contributions to $0\nu \beta \beta$ and constrain the model parameters from the latest experimental bound on such a rare decay process. We find that the new physics contribution to $0\nu \beta \beta$ in such a scenario, particularly the heavy-light neutrino mixing diagrams, can individually saturate the existing experimental bounds, but their contributions to total $0\nu \beta \beta$ half-life cancels each other due to unitarity of the total $6\times 6$ mass matrix. The effective contribution to half-life therefore, arises from the purely left and purely right neutrino and gauge boson mediated diagrams. We find that the parameter space saturating the $0\nu \beta \beta$ bounds remain allowed from the latest experimental bounds on charged lepton flavour violating decays like $\mu \rightarrow e \gamma$. We finally include the bounds from cosmology and supernova to constrain the parameter space of the model.