Impact of dim-6 $\nu$SMEFT operators on low-scale leptogenesis

Abstract

We investigate the impact of higher-dimensional operators on low-scale leptogenesis (LG) via oscillations of right-handed neutrinos within the neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT) and discuss the connection to neutrinoless double beta decay ($0\nu\beta\beta$). Focusing on a dimension-six, lepton number conserving operator, we explore how new interactions can significantly alter the production and equilibration dynamics of right-handed neutrinos. We derive the relevant quantum kinetic equations incorporating both renormalizable and non-renormalizable interactions and perform a comprehensive numerical analysis for benchmark scenarios in both the oscillatory and overdamped regimes. Our results reveal that even in the absence of explicit lepton number violation by the operator, it can enhance or suppress the baryon asymmetry of the universe (BAU) by several orders of magnitude, depending on the EFT scale. We further connect these effects to predictions for $0\nu\beta\beta$ decay, demonstrating that the same operator can lead to enhanced decay rates, potentially within reach of the next generation of experiments. Our findings indicate that the observation of $0\nu\beta\beta$ could rule out a large part of the parameter space for successful low-scale LG within the $\nu$SMEFT, implying low RHN masses and low reheating temperatures.