Standard model confronting new results for ε′/ε Original Research Article

We analyze the CP-violating ratio ε′/ε in the Standard Model in view of the new KTeV results. We review the present status of the most important non-perturbative parameters B6(1/2), B8(3/2), B̂K and of the strange quark mass ms. We also briefly discuss the issues of final state interactions and renormalization scheme dependence. Updating the values of the CKM parameters, of mt and ΛMS(4) and using Gaussian errors for the experimental input and flat distributions for the theoretical parameters we find ε′/ε substantially below the NA31 and KTeV data: ε′/ε=(7.7+6.0−3.5)×10−4 and ε′/ε=(5.2+4.6−2.7)×10−4 in the NDR and HV renormalization schemes respectively. A simple scanning of all input parameters gives on the other hand 1.05×10−4⩽ε′/ε⩽28.8×10−4 and 0.26×10−4⩽ε′/ε⩽22.0×10−4 respectively. Analyzing the dependence on various parameters we find that only for extreme values of B6(1/2), B8(3/2) and ms as well as suitable values of CKM parameters and ΛMS(4), the ratio ε′/ε can be made consistent with data. We analyze the impact of these data on the lower bounds for Im VtdVts∗, Br(KL→π0νν̄), Br(KL→π0e+e−)dir and on tanβ in the two-Higgs doublet Model II.