Electroweak Baryogenesis and the Standard Model Effective Field Theory

TL;DR

This paper explores electroweak baryogenesis using the Standard Model Effective Field Theory, highlighting the limitations of the EFT approach in describing the phase transition and CP violation.

Contribution

It analyzes the impact of higher-dimensional operators on baryogenesis and identifies where the effective field theory expansion breaks down.

Findings

Higher-order dimension-eight corrections significantly alter matter-antimatter asymmetry.

The EFT expansion fails in the Higgs sector for a first-order phase transition.

Breakdown of EFT affects the CP-violating sector, challenging its applicability.

Abstract

We investigate electroweak baryogenesis within the framework of the Standard Model Effective Field Theory. The Standard Model Lagrangian is supplemented by dimension-six operators that facilitate a strong first-order electroweak phase transition and provide sufficient CP violation. Two explicit scenarios are studied that are related via the classical equations of motion and are therefore identical at leading order in the effective field theory expansion. We demonstrate that formally higher-order dimension-eight corrections lead to large modifications of the matter-antimatter asymmetry. The effective field theory expansion breaks down in the modified Higgs sector due to the requirement of a first-order phase transition. We investigate the source of the breakdown in detail and show how it is transferred to the CP-violating sector. We briefly discuss possible modifications of the effective field theory framework.