ar X iv : h ep - p h / 01 07 27 6 v 1 2 6 Ju l 2 00 1 1 CP Violation in SUSY

Supersymmetry exhibts new sources of CP violation. We discuss the implications of these new contributions to CP violation both in the K and B physics. We show that CP violation puts severe constraints on low energy SUSY, but it represents also a promising ground to look for signals of new physics. CP violation has major potentialities to exhibit manifestations of new physics beyond the standard model. Indeed, it is quite a general feature that new physics possesses new CP violating phases in addition to the Cabibbo–Kobayashi– Maskawa (CKM) phase (δ CKM) or, even in those cases where this does not occur, δ CKM shows up in interactions of the new particles, hence with potential departures from the SM expectations. Moreover, although the SM is able to account for the observed CP violation in the kaon system , we cannot say that we have tested so far the SM predictions for CP violation. The detection of CP violation in B physics will constitute a crucial test of the standard CKM picture within the SM. Again, on general grounds, we expect new physics to provide departures from the SM CKM scenario for CP violation in B physics. A final remark on reasons that make us optimistic in having new physics playing a major role in CP violation concerns the matter–antimatter asymmetry in the universe. Starting from a baryon– antibaryon symmetric universe, the SM is unable to account for the observed baryon asymmetry. The presence of new CP–violating contributions when one goes beyond the SM looks crucial to produce an efficient mechanism for the generation of a satisfactory ∆B asymmetry. The above considerations apply well to the new physics represented by low–energy supersymmet-ric extensions of the SM. Indeed, as we will see * Present address Dep FísicaTè orica, U deVaì encia, Spain below, supersymmetry introduces CP violating phases in addition to δ CKM and, even if one envisages particular situations where such extra– phases vanish, the phase δ CKM itself leads to new CP–violating contributions in processes where SUSY particles are exchanged. CP violation in B decays has all potentialities to exhibit departures from the SM CKM picture in low–energy SUSY extensions, although, as we will discuss, the de-tectability of such deviations strongly depends on the regions of the SUSY parameter space under consideration. In any MSSM, at least two new " genuine " SUSY CP–violating phases are present. They originate from the …