Electroweak Baryogenesis and New TeV Fermions

Abstract

New fermions, strongly coupled to the Standard Model Higgs boson provide a well motivated extension of the Standard Model (SM). In this work we show that, once new physics at heavier scales is added to stabilize the Higgs potential, such an extension of the SM can strengthen the first order electroweak phase transition and make the electroweak baryogenesis mechanism feasible. We propose a SM extension with TeV Higgsinos, Winos and Binos that satisfy the following properties: a) The electroweak phase transition is strong enough to avoid sphaleron erasure in the broken phase for values of the Higgs mass mH < 300 GeV; b) It provides large CP-violating currents that lead to the observed baryon asymmetry of the Universe for natural values of the CP-violating phase; c) It also provides a natural Dark Matter candidate that can reproduce the observed dark matter density; d) It is consistent with electroweak precision measurements; e) It may arise from a softly broken supersymmetric theory with an extra (asymptotically free) gauge sector; e) It may be tested by electron electric dipole moment experiments in the near future.

Figures (12)

• Figure 1: Curves of constant $\phi_c/T_c=1$ and $m_H = 120$ GeV, for a fermion with mass $m^2=\mu^2+h^2\phi^2$ and $g$ degrees of freedom. From top to bottom the curves correspond to $h=1.5$, $2$, $2.5$, and $3$.
• Figure 2: The free energy at different temperatures for $h=2$, $m_H=120$ GeV and $\mu =-M\simeq 200$ GeV.
• Figure 3: $\phi_c/T_{c}$ for $m_H=$ 120 GeV and $h=2$ as a function of $M=- \mu$ in GeV.
• Figure 4: Yukawa coupling $h$ necessary to get $\phi_c/T_{c}=1$ for $m_H=$ 120 GeV as a function of $M=- \mu$ in GeV.
• Figure 5: Contours of $\phi_c/T_c=1$ in the $(M,m_H)$-plane for $h=1.6,2,2.5,3$ and $M = - \mu$. The vertical line corresponds to the experimental lower bound, for a SM-like Higgs, of $m_H=115$ GeV.