Systematic approach to thermal leptogenesis

TL;DR

This paper develops a quantum field theory-based framework for thermal leptogenesis, deriving kinetic equations that include medium effects, quantum-statistical corrections, and consistent treatment of decay and scattering processes.

Contribution

It introduces a systematic quantum field theoretical approach to leptogenesis, improving upon conventional methods by including medium corrections and quantum-statistical effects.

Findings

Derived quantum kinetic equations for leptogenesis.

Connected scattering processes to higher-loop effective actions.

Included medium effects and thermal masses in decay and scattering amplitudes.

Abstract

In this work we study thermal leptogenesis using non-equilibrium quantum field theory. Starting from fundamental equations for correlators of the quantum fields we describe the steps necessary to obtain quantum kinetic equations for quasiparticles. These can easily be compared to conventional results and overcome conceptional problems inherent in the canonical approach. Beyond CP-violating decays we include also those scattering processes which are tightly related to the decays in a consistent approximation of fourth order in the Yukawa couplings. It is demonstrated explicitly how the S-matrix elements for the scattering processes in the conventional approach are related to two- and three-loop contributions to the effective action. We derive effective decay and scattering amplitudes taking medium corrections and thermal masses into account. In this context we also investigate CP-violating Higgs decay within the same formalism. From the kinetic equations we derive rate equations for the lepton asymmetry improved in that they include quantum-statistical effects and medium corrections to the quasiparticle properties.