Finite Number Density Corrections to Leptogenesis

TL;DR

This paper develops a quantum field theoretical approach to leptogenesis, revealing how quantum statistical effects, especially Bose enhancement, influence lepton asymmetry generation under different washout conditions.

Contribution

It introduces a CTP formalism-based kinetic equation framework for leptogenesis, incorporating quantum statistical corrections and real intermediate state subtraction.

Findings

Quantum statistical corrections can significantly enhance asymmetry in weak washout regimes.

In strong washout regimes, quantum corrections are negligible.

The approach aligns with CPT-theorem and extends Boltzmann methods.

Abstract

We derive and solve kinetic equations for leptogenesis within the Closed Time Path (CTP) formalism. It is particularly emphasised how the procedure of real intermediate state subtraction familiar from the Boltzmann approach is realised within the CTP framework; and we show how in time-independent situations, no lepton asymmetry emerges, in accordance with the CPT-theorem. The CTP approach provides new quantum statistical corrections from evaluating the loop integrals. These lead to an enhancement of the asymmetry that is originating from the Bose statistics of the Higgs particles. To quantify this effect, we define and evaluate an effective CP-violating parameter. We also solve the kinetic equations and show explicitly that the new quantum statistical corrections can be neglected in the strong washout regime, while, depending on initial conditions, they can be very sizable for weak washout.