Electroweak Baryogenesis in a Scalar-Assisted Vector-Like Fermion Model

TL;DR

This paper proposes an extension of the standard model with a scalar-assisted vector-like fermion to achieve electroweak baryogenesis, introducing new CP violation sources and analyzing phase transition conditions.

Contribution

It introduces a novel scalar-assisted vector-like fermion model that enables electroweak baryogenesis through enhanced CP violation and a strongly first-order phase transition.

Findings

Large trilinear Higgs-scalar mass term controls the potential barrier.

Large scalar quartic couplings and moderate mixing are favored.

Parameter space can be tested at the Run 2 LHC.

Abstract

We extend the standard model to a scalar-assisted vector-like fermion model to realize electroweak baryogenesis. The extended Cabbibo-Kobayashi-Maskawa matrix, due to the mixing among the vector-like quark and the standard model quarks, provides additional sources of the CP violation. Together with the enhancement from large vector-like quark mass, a large enough baryon-to-photon ratio could be obtained. The strongly first-order phase transition could be realized via the potential barrier which separate the broken minimum and the symmetric minimum in the scalar potential. We investigate in detail the one-loop temperature-dependent effective potential, and perform a random parameter scan to study the allowed parameter region that satisfies the strongly first order phase transition criteria $v_c \ge T_c$. Several distinct patterns of phase transition are classified and discussed. Among these patterns, large trilinear mass term between the Higgs boson and the scalar is preferred, for it controls the width of the potential barrier. Our results indicate large quartic scalar couplings, and moderate mixing angle between the Higgs boson and the new scalar. This parameter region could be further explored at the Run 2 LHC.