Gravitational wave complementarity and impact of NANOGrav data on gravitational leptogenesis

In seesaw mechanism, if right handed (RH) neutrino masses are generated dynamically by a gauged U(1) symmetry breaking, a stochastic gravitational wave background (SGWB) sourced by a cosmic string network could be a potential probe of leptogenesis. We show that the leptogenesis mechanism that facilitates the dominant production of lepton asymmetry via the quantum effects of right-handed neutrinos in gravitational background, can be probed by GW detectors as well as next-generation neutrinoless double beta decay (0νββ) experiments in a complementary way. We infer that for a successful leptogenesis, an exclusion limit on f − ΩGWh2 plane would correspond to an exclusion on the |mββ| − m1 plane as well. We consider a normal light neutrino mass ordering and discuss how recent NANOGrav pulsar timing data (if interpreted as GW signal) e.g., at 95% CL, would correlate with the potential discovery or null signal in 0νββ decay experiments.