Testable leptogenesis and $0\nu\beta\beta$ decay in extended seesaw model

TL;DR

This paper explores how an extended low-scale seesaw model with sterile neutrinos can simultaneously produce observable neutrinoless double beta decay signals and generate the universe's baryon asymmetry through viable leptogenesis.

Contribution

It demonstrates that in an extended inverse seesaw framework, both observable $0 uetaeta$ decay and successful low-scale leptogenesis can coexist with TeV-scale right-handed neutrinos.

Findings

Sterile neutrinos can enhance $0 uetaeta$ decay signals.

Low-scale leptogenesis remains viable with extended seesaw parameters.

Future ton-scale experiments could detect sterile neutrino signatures.

Abstract

We investigate the possibility of observable neutrinoless double beta decay $( 0 \nu \beta\beta)$ and viable leptogenesis within a low-scale extended inverse seesaw mechanism with additional sterile neutrinos. General effective field theory (EFT) considerations suggest that if there are experimentally observable signatures in $0 \nu \beta \beta$-decay and a lepton asymmetry generated by heavy right-handed neutrino decays, thermal leptogenesis is likely to be unviable. However, in this work, we show that in the context of low-scale leptogenesis, one can obtain the observed baryon asymmetry of the universe and observable signatures of $0 \nu \beta \beta$ decay in the presence of additional sterile neutrinos. In this framework, the light neutrino masses are suppressed by the extended seesaw parameter, $\mu$, thereby allowing for $\mathcal{O}(10\, \mathrm{TeV})$ right-handed (RH) neutrinos, while avoiding small Yukawa couplings as in other neutrino mass models and near degeneracies in the RH neutrino spectrum as required by the low-scale leptogenesis paradigm. Contributions to the $0 \nu \beta \beta$-decay rate from additional sterile neutrinos can be appreciable, while the corresponding contributions to the early universe lepton asymmetry washout rate are suppressed by other parameters not entering the $0 \nu \beta \beta$-decay amplitudes. We show that for keV-MeV scale, sterile neutrinos future ton-scale $0\nu\beta\beta$-decay experiments offer potential signals while maintaining viable leptogenesis.