ep - p h / 02 02 22 8 v 1 2 5 Fe b 20 02 SUSY contributions to the charge asymmetry in K ± → π ± l + l − decays
نویسنده
چکیده
We analyse the contributions to the charge asymmetry in K → πll decays induced by gluino-exchange diagrams in the context of supersymmetric models with generic flavour couplings. We show that sizeable deviations with respect to the Standard Model are possible only under special circumstances. Within this scenario we set an upper limit of about 10 for the relative charge asymmetry – integrated for Ml+l− > 2Mπ – of both muon and electron channels. We also show that this limit is close to saturating a modelindependent upper bound on the charge asymmetry derived from the present constraints on Γ(KL → πll). I. CP violation is one of most interesting and least known aspects of particle physics. The recent results of KTeV [1] and NA48 [2] about ε/ε have unambiguously shown the existence of CP violation in |∆S| = 1 transitions (the so-called direct CP violation) and ruled out superweak scenarios. The experimental measurements of ε/ε are generally compatible with the theoretical expectations within the Standard Model (SM) [3]. Nevertheless, the latter are affected by sizeable theoretical uncertainties, and it is difficult to constrain non-standard effects. At the moment the theoretical uncertainties on ε/ε are so large that we cannot even exclude that this observable is completely dominated by new physics (NP) contributions. Given this situation, it is highly desirable to obtain new independent information about CP violation in |∆S| = 1 transitions. Among direct-CP-violating observables, particularly interesting are those accessible in rare decays. In these processes the smallness of the SM contribution leads to identifying more easily a possible large NP effect, whereas the simplicity of the hadronic structure helps us to keep under control the theoretical uncertainties [4]. An observable that satisfies these requirements is the charge asymmetry in K → πll, defined as
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