Soft leptogenesis in the NMSSM with a singlet right-handed neutrino superfield

TL;DR

This paper investigates soft leptogenesis within the NMSSM extended by a right-handed neutrino superfield, demonstrating non-zero CP asymmetry at tree-level due to unique decay processes and singlet scalar VEVs, offering a novel mechanism for baryogenesis.

Contribution

It introduces a new soft leptogenesis mechanism in the NMSSM with a right-handed neutrino, showing CP asymmetry at tree-level without thermal effects, unlike in MSSM extensions.

Findings

CP asymmetry is non-zero at tree-level without thermal effects.

3-body decay of sneutrino violates lepton number at tree-level.

Complex VEV of singlet scalar enables CP asymmetry with real NMSSM parameters.

Abstract

In this work, we explore soft leptogenesis in the NMSSM framework extended by a right-handed neutrino superfield. We calculate the CP asymmetry, $\varepsilon$, and find it to be non-zero at tree-level without using thermal effects for the final state particles. This is in contrast to soft leptogenesis in the MSSM extended by a right-handed neutrino superfield where thermal effects are essential. The difference arises due to the presence of a 3-body decay of the sneutrino in the NMSSM that violates lepton number at tree-level. Apart from this, we also find that $\varepsilon\neq 0$ if the additional singlet scalar has a complex vacuum expectation value while all the other NMSSM parameters including the soft SUSY breaking ones relevant for CP asymmetry remain real. We estimate the order of magnitudes of these parameters to produce sufficient baryon asymmetry of the Universe.