Abstract :
Firstly, we use the recent ALEPH/OPAL data on the V−A spectral functions for fixing the continuum threshold with which the first and second Weinberg sum rules should be satisfied in the chiral limit. Then, we predict the values of the low-energy constants mπ+−mπ0, L10, and test the values of the electroweak kaon penguin matrix elements 〈Q3/28,7〉2π obtained from DMO-like sum rules. Secondly, we use the data on the τ-total hadronic width Rτ,V/A for extracting 〈Q83/2〉2π, in the MS-scheme, and propose some new sum rules for 〈Q73/2〉2π in the chiral limit, where the latter require more accurate data for the spectral functions near the τ-mass. Thirdly, we analyze the effects to the matrix element 〈Q61/2〉2π, of the S2≡(ūu+d̄d) component of the I=0 scalar meson, with its parameters fixed from QCD spectral sum rules. Our results should stimulate a further attention on the role of the (expected large) gluonium component of the I=0 scalar meson and of the associated operator in the K→ππ amplitude. Finally, using our previous determinations, we deduce, in the Standard Model (SM), the conservative upper bound for the CP-violating ratio: ϵ′/ϵ⩽(22±9)×10−4, which is in agreement with the present measurements.
