Constraints on the neutrino extension of the Standard Model and baryon asymmetry of the Universe

TL;DR

This paper investigates how heavy neutral leptons influence charged lepton flavor violation and the baryon asymmetry of the Universe, deriving new constraints on their parameters by linking these phenomena.

Contribution

It establishes relations between cLFV operators with non-zero active neutrino masses and non-degenerate HNLs, strengthening existing constraints and connecting baryon asymmetry to cLFV effects.

Findings

Strengthened constraints on HNL parameters from non-observation of cLFV.

Derived relations between cLFV operators considering realistic neutrino masses.

Linked baryon asymmetry to cLFV operators, imposing new restrictions.

Abstract

Heavy neutral leptons (HNLs) can cause new effective interactions of Standard Model particles, particularly charged lepton flavour violation (cLFV) processes. The non-observation of cLFV processes, therefore, puts constraints on the parameters of the HNLs. We find the relations between the cLFV effective operators in the realistic case when active neutrino masses are non-zero and masses of the HNLs are non-degenerate. This allows us to strengthen the existing cLFV constraints. We also link the baryon asymmetry of the Universe to the same cLFV effective operators, which imposes new restrictions on their values.