Can heavy neutrinos dominate neutrinoless double beta decay?

TL;DR

This paper investigates whether heavy neutrinos in type-I seesaw models can be the main contributors to neutrinoless double beta decay, especially when light neutrino contributions cancel out, considering one-loop corrections and specific model limits.

Contribution

It provides a comprehensive analysis of heavy neutrino dominance in neutrinoless double beta decay within type-I seesaw models, including one-loop effects and parameter space constraints.

Findings

Heavy neutrinos can dominate decay only in specific parameter limits.

In inverse seesaw, heavy neutrino masses around 5 GeV are favored.

Extended seesaw models allow larger parameter regions with hierarchical heavy neutrino spectra.

Abstract

We study whether a dominant contribution to neutrinoless double beta decay coming from extra heavy degrees of freedom, introduced to generate the light neutrino masses, can dominate over the light neutrino contribution. It has been shown that this may occur at tree-level if the light neutrino contribution partially cancels out. Here we focus on this case, specifically in the context of type-I seesaw models paying special attention to the one-loop corrections to light neutrino masses, their contribution to the process and correlation with the heavy sector. We perform a general analysis without restricting the study to any particular region of the parameter space, although interesting limits associated with inverse and extended seesawlike models are discussed in more detail. It turns out that the heavy neutrinos can dominate the process only in those limits. For the inverse seesaw limit, we find a very constrained allowed region of the parameter space, with heavy neutrino masses around 5 GeV. The extended seesaw case allows for a larger region, but in general, a hierarchical spectrum of heavy neutrinos with masses above and below $\sim100$ MeV is required.