TeV Scale Left-Right Symmetry and Large Mixing Effects in Neutrinoless Double Beta Decay

Abstract

We analyze various contributions to neutrinoless double beta decay ($0\hat{I}½{\hat{I}}^2{\hat{I}}^2$) in a TeV-scale Left-Right Symmetric Model (LRSM) for type-I seesaw dominance. We find that the momentum-dependent effects due to $W_L-W_R$ exchange ($\hat{I}»$-diagram) and $W_L-W_R$ mixing ($\hat{I}\cdot$-diagram) could give dominant contributions to the $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$ amplitude in a wide range of the LRSM parameter space. In particular, for a relatively large $W_L-W_R$ mixing, the $\hat{I}\cdot$-contribution by itself could saturate the current experimental limit on the $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$ half-life, thereby providing stringent constraints on the relevant LRSM parameters, complementary to the indirect constraints derived from lepton flavor violating observables. In a simplified scenario parametrized by a single light-heavy neutrino mixing, the inclusion of the $\hat{I}»$ and $\hat{I}\cdot$ contributions leads to significantly improved $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$ constraints on the light-heavy neutrino mixing as well as on the $W_L-W_R$ mixing parameters. We also present a concrete TeV-scale LRSM setup, where the mixing effects are manifestly enhanced, and discuss the interplay between $0\hat{I}½{\hat{I}}^2{\hat{I}}^2$, lepton flavor violation and electric dipole moment constraints.

33 pages, 7 figures, 2 tables