Cuts, Cancellations and the Closed Time Path: The Soft Leptogenesis Example

TL;DR

This paper demonstrates that when all quantum-statistical effects are properly included, soft leptogenesis does not produce a net lepton asymmetry, highlighting the importance of comprehensive quantum statistical treatment in baryogenesis models.

Contribution

It provides a complete quantum-statistical analysis of soft leptogenesis, correcting previous incomplete approaches and establishing a more accurate framework for leptogenesis calculations.

Findings

No net lepton asymmetry is generated in soft leptogenesis with full quantum effects.

Resonant mixing of sneutrinos may contribute to asymmetry, but other effects cancel out.

The analysis offers guidance for constructing viable baryogenesis models.

Abstract

By including all leading quantum-statistical effects at finite temperature, we show that no net asymmetry of leptons and sleptons is generated from soft leptogenesis, save the possible contribution from the resonant mixing of sneutrinos. This result contrasts with different conclusions appearing in the literature that are based on an incomplete inclusion of quantum statistics. We discuss vertex and wave-function diagrams as well as all different possible kinematic cuts that nominally lead to CP-violating asymmetries. The present example of soft leptogenesis may therefore serve as a paradigm in order to identify more generally applicable caveats relevant to alternative scenarios for baryogenesis and leptogenesis, and it may provide useful guidance in constructing viable models.