Quasi-Dirac Heavy Neutral Leptons in the Left-Right Symmetric Model

Abstract

We discuss the phenomenology of a pair of degenerate GeV-scale Heavy Neutral Leptons within the Left-Right Symmetric Model (LRSM) framework, with the third fermion serving as a dark matter candidate. We highlight the potential of the recently approved SHiP experiment to test the existence of the light DM species, and the signatures of lepton number violation as a possible experimental probe of the model in various experiments. Our findings include concrete predictions, in some part of the model's parameter space, for the effective right-handed couplings $(V^{R}_{e})^2:(V^{R}_{\mu})^2:(V^{R}_{\tau})^2 = 0.16:0.47:0.38$ (normal neutrino hierarchy), $0.489 : 0.22 : 0.30$ (inverted hierarchy) of the degenerate pair.