CP Violation In Supersymmetric Models Research Articles

CP violation in supersymmetric models with Hermitian Yukawa couplings andA-terms

We analyse the CP violation in supersymmetric models with Hermitian Yukawa and trilinear couplings. We show that Hermitian Yukawa matrices can be implemented in supersymmetric models with SU(3) flavor symmetry. An important feature of this class of models is that the supersymmetric contributions to the EDM of the neutron and mercury atom are suppressed. In this framework, epsilon_K can be saturated by a small non--universality of the soft scalar masses through the gluino contribution. We perform a detailed analysis for the supersymmetric contributions to epsilon'/epsilon. Although, the gluino contribution is found to be negligible due to a severe cancellation between LR and RL mass insertions, the chargino contribution can be significant and accommodate the experimental results. Additionally, we find that the SUSY contributions to epsilon'/epsilon from the effective \bar{s}dZ vertex and the \Delta I =3/2 operators are insignificant. We point out that the standard model gives the leading contribution to the CP asymmetry in B -> \psi K_S decay, while the dominant chargino contribution to this asymmetry is < 0.2 . Thus, no constraint is set on the non--universality of this model by the recent BaBar and Belle measurements.

New limit on the permanent electric dipole moment of 199Hg.

We present the first results of a new search for a permanent electric dipole moment of the 199Hg atom using a UV laser. Our measurements give d(199Hg) = -(1.06+/-0.49+/-0.40)x10(-28)e cm. We interpret the result as an upper limit absolute value [d(199Hg)]<2.1x10(-28)e cm (95% C.L.), which sets new constraints on theta bar;(QCD), chromo-EDMs of the quarks, and CP violation in supersymmetric models.

Probing spontaneous CP-violation in supersymmetric models via B-decays

We study implications of spontaneous CP-violation in minimal susy models for CP-asymmetries in rare B, B ̄ -decays. In particular, we estimate characteristic values of the angles of the unitarity triangle and show that sizable CP-violating effects result from B− B ̄ mixing only. Significant deviations from the SM predictions are pointed out.

Implications of the strange spin of the nucleon for the neutron electric dipole moment in supersymmetric theories

Supersymmetric model contributions to the neutron electric dipole moment arise via quark electric dipole moment operators, whose matrix elements are usually calculated using the Naive Quark Model (NQM). However, experiments indicate that the NQM does not describe well the quark contributions Δq to the nucleon spin, and so may provide misleading estimates of electric dipole operator matrix elements. Taking the Δq from experiment, we indeed find consistently smaller estimates of the neutron electric dipole moment for given values of the supersymmetric model parameters. This weakens previous constraints on CP violation in supersymmetric models, which we exemplify analytically in the case where the lightest supersymmetric particle (LSP) is a U(1) gaugino B , and display numerically for other LSP candidates.

Spontaneous CP violation in supersymmetric models with four Higgs doublets.

We consider supersymmetric extensions of the standard model with two pairs of Higgs doublets. We study the possibility that CP violation is generated spontaneously in the scalar sector via vacuum expectation values (VEVs) of the Higgs fields. Using a simple geometrical interpretation of the minimum conditions we prove that the minimum of the tree-level scalar potential for these models is allways real. We show that complex VEVs can appear once radiative corrections and/or explicit {\it soft} CP violating terms are added to the effective potential.

B 0 − B̄ 0 mixing and related CP violation in supersymmetric models

We analyze the supersymmetric contributions to B d 0 − B̄ d 0 mixing. For squark and gluino masses which respect the bounds coming from the CERN pp̄ collider, the supersymmetric contribution turns out to be substantially smaller than the corresponding standard model prediction. However, we suggest that the presence of supersymmetry may sizeably contribute to the observability of large CP asymmetries related to the mixing.