Perspectives for tests of neutrino mass generation at the GeV scale: Experimental reach versus theoretical predictions

TL;DR

This paper evaluates the potential of future experiments to detect heavy neutral leptons at the GeV scale, comparing generic and flavor symmetry models, and emphasizing the importance of flavor-dependent coupling measurements for model discrimination.

Contribution

It provides a comparative analysis of parameter space predictions for HNL detection in different neutrino mass models, highlighting experimental reach and the role of flavor measurements.

Findings

Generic models predict detectable parameter space within future experiment reach.

Flavor symmetry models offer more specific predictions, some of which can be excluded.

Measuring flavor-dependent couplings is crucial for distinguishing models.

Abstract

We discuss the parameter space reach of future experiments searching for heavy neutral leptons (HNLs) at the GeV scale in terms of neutrino mass models with three HNL generations. We focus on two classes of models: Generic assumptions (such as random mass matrices or the Casas-Ibarra parameterization) and flavor symmetry-generated models. We demonstrate that the generic approaches lead to comparable parameter space predictions, which tend to be at least partially within the reach of future experiments. On the other hand, specific flavor symmetry models yield more refined predictions, some of these can be more clearly excluded. We also highlight the importance to measure the flavor-dependent couplings of the HNLs as a model discriminator, and we clarify the impact of assumptions frequently used in the literature to show the parameter space reach for the active-sterile mixings.