Electroweak baryogenesis and low energy supersymmetry

Abstract

Electroweak baryogenesis is an interesting theoretical scenario, which demands physics beyond the Standard Model at energy scales of the order of the weak boson masses. It has been recently emphasized that, in the presence of light stops, the electroweak phase transition can be strongly first order, opening the window for electroweak baryogenesis in the MSSM. For the realization of this scenario, the Higgs boson must be light, at the reach of the LEP2 collider. In this article, we compute the baryon asymmetry assuming the presence of non-trivial CP violating phases in the parameters associated with the left-right stop mixing term and the Higgsino mass $μ$. We conclude that a phase $|\sin φ_μ| > 0.01$ and Higgsino and gaugino mass parameters $|μ| \simeq M_2$, and of the order of the electroweak scale, are necessary in order to generate the observed baryon asymmetry.

Figures (3)

• Figure 1: a) One-loop Feynman diagrams contributing to $\langle J_R^{\mu}(z)\rangle$. Here $m_{LR}^2$ indicates the combination $h_t\left(A_t H_2-\mu^{\star}H_1\right)$. b) One-loop diagrams contributing to $\langle J^0_{\widetilde{H}}(z)\rangle$. Here $\mu_a$, $a=1,\cdots,4$ describes the interactions of Higgsinos with gauginos $\widetilde{W}_a$, $a=1,\cdots,3$ and $\widetilde{B}$, $a=4$. More precisely, $\mu_a=g_a \left[ H_1 P_L+\frac{\mu}{|\mu|} H_2 P_R\right]$ where $P_{L(R)}=\frac{1}{2}\left(1\mp \gamma_5\right)$, $g_a=g_2$, $a=1,\cdots,3$, and $g_a=g_1$ for $a=4$.
• Figure 2: Contour plots of constant values of $v(T_c)/T_c$ (solid lines) and $m_H$ in GeV (dashed lines) in the plane $(m_A,\tan\beta)$. We have fixed $m_t=175$ GeV and the values of sypersymmetric parameters: $m_Q=500$ GeV, $m_U=m_U^{\rm crit}$ fixed by the charge and color breaking constraint, and $A_t=\mu/\tan\beta$.
• Figure 3: Contour plot of $|\sin \phi_{\mu}|$ in the plane ($\mu,M_2$) for fixed $n_B/s = 4 \times 10^{-11}$ and $v_{\omega}=0.1$, $L_{\omega}=25/T$, $m_Q=500$ GeV, $m_U=m_U^{\rm crit}$, $\tan\beta=2$ and $A_t=\mu/\tan\beta$.