Implications of baryon asymmetry for the electric dipole moment of the neutron

Abstract

We study baryogenesis at the electroweak phase transition of the universe within the framework of the supersymmetric standard model (SSM) based on N=1 supergravity. This model contains a new source of CP violation in the mass-squared matrices for squarks, which could enable $t$ squarks to mediate the charge transport mechanism for generating baryon asymmetry. The same CP-violating source also induces the electric dipole moment (EDM) of the neutron at the one-loop level. If the new CP-violating phase is not suppressed, it is shown, the $t$-squark transport can lead to baryon asymmetry consistent with its observed value within reasonable ranges of SSM parameters. For these parameter ranges the magnitude of the neutron EDM is predicted to be not much smaller than its present experimental upper bound.

Figures (2)

• Figure 1: The ratio of baryon number to entropy as a function of $m_{3/2}$ for $\alpha=\pi/4$ and $\theta=0$. The values of $v_W$ and $\delta_W$ for curves (i.a)--(ii.b) are given in Table \ref{['tab1']}. The other parameters are taken for $\tan\beta=2$, $|m_H|=100$ GeV, and $T=200$ GeV.
• Figure 2: The electric dipole moment of the neutron as a function of $m_{3/2}$ for $\alpha=\pi/4$ and $\theta=0$. Three curves correspond to three values for ${\tilde{m}}_2$: (i) 200 GeV, (ii) 500 GeV, (iii) 1 TeV. The other parameters are taken for $\tan\beta=2$ and $|m_H|=100$ GeV.