An allowed window for heavy neutral leptons below the kaon mass

TL;DR

This paper identifies an allowed parameter space for heavy neutral leptons below the kaon mass within a Standard Model extension, which can be explored by upcoming experiments like NA62, DUNE, and SHiP.

Contribution

It demonstrates that despite multiple constraints, a viable parameter region for heavy neutral leptons exists below the kaon mass, guiding future experimental searches.

Findings

Allowed parameter space below kaon mass identified

Constraints from neutrino data, BBN, and baryogenesis considered

Future experiments can probe this parameter region

Abstract

The extension of the Standard Model with two gauge-singlet Majorana fermions can simultaneously explain two beyond-the-Standard-model phenomena: neutrino masses and oscillations, as well as the origin of the matter-antimatter asymmetry in the Universe. The parameters of such a model are constrained by the neutrino oscillation data, direct accelerator searches, big bang nucleosynthesis, and requirement of successful baryogenesis. We show that the combination of all these constraints still leaves an allowed region in the parameter space below the kaon mass. This region can be probed by the further searches of NA62, DUNE, or SHiP experiments.