– 1– Fits for K 0

In recent years, K 0 L CP-violation experiments have improved our knowledge of CP-violation parameters and their consistency with the expectations of CP T invariance and uni-tarity. For definitions of K 0 L CP-violation parameters and a brief discussion of the theory, see the article " CP Violation " by L. Wolfenstein in the Reviews, Tables, and Plots section of this Review. This note describes our two types of fits for the CP-violation parameters in K 0 L → π + π − and π 0 π 0 decay, one for the phases φ +− and φ 00 jointly with ∆m and τ S , and the other for the amplitudes |η +− | and |η 00 | jointly with the K 0 L → ππ branching fractions. In this edition, phase fits are done without and with the assumption of CPT invariance, the latter giving a significant improvement in the precision of ∆m and τ S. data: This is a joint fit to the data on φ +− , φ 00 , the phase difference ∆φ = φ 00 – φ +− , the K 0 L – K 0 S mass difference ∆m, and the K 0 S mean life τ S , including the effects of correlations. Measurements of φ +− and φ 00 are highly correlated with ∆m and τ S. Some measurements of τ S are correlated with ∆m. The correlations are given in the footnotes of the φ +− and φ 00 sections of the K 0 L Particle Listings and the τ S section of the K 0 S Particle listings. In editions of the Review prior to 1996, we adjusted the experimental values of φ +− and φ 00 to account for correlations with ∆m and τ S but did not include the effects of these correlations when evaluating ∆m and τ S. In 1996, we introduced a joint fit including these correlations. In the joint fit, the φ +− measurements have a strong influence on the fitted value of ∆m. This is because the CERN NA31 vacuum regenera-tion experiments (CAROSI 90 [1] and GEWENIGER 74B [2]), the Fermilab E773/E731 regenerator experiments (SCHWIN-GENHEUER 95 [3] and GIBBONS 93 [4]), and the CPLEAR K 0 – K 0 asymmetry experiment (APOSTOLAKIS 99C [5]) have very different dependences of φ +− on ∆m, as can be seen from their diagonal bands e, d, b, …