Introduction to Baryo- and Leptogenesis

Abstract

Course presented at the ITEP School 2005. These notes aim at an introductory presentation, reviewing in a not-too-technical way the fundamental concepts involved in the baryo/leptogenesis search for the origin of the current excess of matter over antimatter.

Although the title of the course was “leptogenesis”, it starts with reviewing the standard approach through direct baryogenesis, and later explains why leptogenesis is now preferred.

These notes do not aim at being exhaustive, and numerous alternatives to the generation of the baryon number of the universe are not covered.

Keywords:

• Lepton number
• Baryon number
• Leptogenesis
• Baryogensis

Acknowledgements

A first series of lectures (rather more general) was given at the “Ecole de Gif” hold in Strasbourg in 2002. These were updated for a more topical presentation at the ITEP School 2005. I wish to thank the organizers of both meetings (and in particular Daniel Bloch, Misha Vysotsky and Michael Danilov) for their invitation and constant encouragements. On a more formal side, I want to thank the IISN (Communauté française de Belgique) and the Belgian Federal Science Policy Office (under IAP V/27 Fundamental Interactions) for their funding.

Notes

Just a side note here: in the case of inflation, the initial density of particles is diluted by the expansion, and becomes negligeable. The following re-heating mechanism may later couple more strongly to some particles than others, possibly resulting in non-thermal distributions, particularly for very weakly coupled sectors.