Quasi-degenerate heavy neutral leptons in the left-right symmetric model

This is the authors' abstract. We don't add key points for this paper.

A bstract 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 a light dark matter species, and signatures of lepton number violation as a possible experimental probe of the model in various experiments. Our findings include concrete predictions for the effective right-handed couplings (VₑR)² V e R 2 : (VμR)² V μ R 2 : (VτR)² V τ R 2 = 0.16 : 0.47 : 0.38 (normal neutrino hierarchy), 0.489 : 0.22 : 0.30 (inverted hierarchy) of the degenerate HNL pair, and (VₑR)² V e R 2 : (VμR)² V μ R 2 : (VτR)² V τ R 2 = 0 . 68 : 0 . 07 : 0 . 24 (normal), 0.02 : 0.57 : 0.41 for the dark matter candidate.