Mixing-induced CP violating sources for electroweak baryogenesis from a semiclassical approach

TL;DR

This paper investigates how flavor mixing contributes to CP violation in electroweak baryogenesis using a semiclassical approach, revealing a new dominant source under certain conditions.

Contribution

It introduces a generalized semiclassical WKB method to identify mixing-induced CP violation sources from off-diagonal particle currents during bubble wall passage.

Findings

Mixing-induced CP violation sources are first order in Higgs condensate derivatives.

These sources are oscillation suppressed but can dominate over semiclassical force contributions.

Numerical analysis in the MSSM shows parameter regions where mixing-induced sources are significant.

Abstract

The effects of flavor mixing in electroweak baryogenesis is investigated in a generalized semiclassical WKB approach. Through calculating the nonadiabatic corrections to the particle currents it is shown that extra CP violation sources arise from the off-diagonal part of the equation of motion of particles moving inside the bubble wall. This type of mixing-induced source is of the first order in derivative expansion of the Higgs condensate, but is oscillation suppressed. The numerical importance of the mixing-induced source is discussed in the Minimal Supersymmetric Standard Model and compared with the source term induced by semiclassical force. It is found that in a large parameter space where oscillation suppression is not strong enough, the mixing-induced source can dominate over that from the semiclassical force.