Bonn 2010 – scientific programme

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T: Fachverband Teilchenphysik

T 22: Neutrinophysik (Theorie) II

T 22.6: Talk

Tuesday, March 16, 2010, 18:00–18:15, HG XV

Finite Density Aspects of Leptogenesis — Mathias Garny², •Andreas Hohenegger¹, Alexander Kartavtsev¹, and Manfred Lindner¹ — ¹Max-Planck-Institut für Kernphysik — ²Technische Universität München

Leptogenesis scenarios are based on the out-of-equilibrium decay of heavy Majorana neutrinos. This process takes place in the early universe at very high temperatures and a deviation from equilibrium is a fundamental requirement for the formation of the asymmetry. The equations used for its description originate from classical Boltzmann equations, which were refined using thermal propagators in the computation of the CP-violating parameter. In view of the basic restrictions of Boltzmann equations, it is desirable to develop an approach which uses non-equilibrium quantum field theory as starting point. On the other hand, it is simpler to solve Boltzmann equations rather than the corresponding quantum field theoretical ones. Therefore, we use modified Boltzmann equations which are derived from first principles in the Kadanoff-Baym formalism. The results found for a simple toy model are applied to a popular phenomenological scenario by analogy. This approach uncovers the structure of the corrected Boltzmann equations and leads to a new result for the form of the thermal contributions to the CP-violating parameter, so that the established derivation must be reconsidered. In contrast to the conventional result, the new form predicts an enhancement of the asymmetry even in the limit of massless decay products.