Supergauge interactions and electroweak baryogenesis

TL;DR

This paper develops a comprehensive framework for understanding supersymmetric electroweak baryogenesis, focusing on transport dynamics and chemical potential equilibration, with implications for the MSSM and beyond.

Contribution

It generalizes existing diffusion models to distinguish particle and superpartner chemical potentials, testing superequilibrium assumptions in supersymmetric models.

Findings

Superequilibrium is generally maintained in the MSSM due to Yukawa interactions.

Analytic and numerical methods are provided for regions with incomplete equilibration.

Discussion of broken superequilibrium scenarios relevant for extended models.

Abstract

We present a complete treatment of the diffusion processes for supersymmetric electroweak baryogenesis that characterizes transport dynamics ahead of the phase transition bubble wall within the symmetric phase. In particular, we generalize existing approaches to distinguish between chemical potentials of particles and their superpartners. This allows us to test the assumption of superequilibrium (equal chemical potentials for particles and sparticles) that has usually been made in earlier studies. We show that in the Minimal Supersymmetric Standard Model, superequilibrium is generically maintained -- even in the absence of fast supergauge interactions -- due to the presence of Yukawa interactions. We provide both analytic arguments as well as illustrative numerical examples. We also extend the latter to regions where analytical approximations are not available since down-type Yukawa couplings or supergauge interactions only incompletely equilibrate. We further comment on cases of broken superequilibrium wherein a heavy superpartner decouples from the electroweak plasma, causing a kinematic bottleneck in the chain of equilibrating reactions. Such situations may be relevant for baryogenesis within extensions of the MSSM. We also provide a compendium of inputs required to characterize the symmetric phase transport dynamics.