The proposed project addresses the computation of quantumchromodynamical three-loop radiative corrections to the mixing of the neutral Kaon with its antiparticle. The goal is the reduction of the perturbative uncertainty in the prediction of the CP-violating quantity epsilon_K to below 5%. This accuracy is needed to keep up with the anticipated progress in ongoing computations of the non-perturbative hadronic parameter B_K using lattice QCD. The currently known two-loop result for epsilon_K has a perturbative uncertainty of roughly 8%. Its reduction requires the calculation of three-loop corrections to the short-distance QCD coefficients eta_3and eta_1, which involve the low scale of the charm mass and are therefore prone to large QCD corrections.
The coordinator of the proposal is experienced with such calculations; a similar calculation for a rare Kaon decay is currently underway. A computation of epsilon_K with high accuracy permits an important high-precision test of the Kobayashi-Maskawa mechanism of CP violation: While current experiments at B-meson factories provide us with accurate data on the CP-violating phase in the Cabibbo-Kobayashi-Maskawa matrix, one wants to check whether the same phase also explains the observed amount of CP violation in the Ka on system, because neutral Kaon mixing is very sensitive to new physics.
Call for proposal
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