We report results from the analysis of the K± → Π+Π-e±v (Ke4)decay by the NA48/2 collaboration at the CERN SPS, based on the total statistics of 1.13 million decays collected in 2003-2004. The hadronic form factors in the S- and P-wave and their variation with energy are obtained. The phase difference between the S- and P-wave states of the ππ system is accurately measured and allows a precise determination of a00 and a02, the I = 0 and I = 2 S-wave ππ scattering lengths: a00 = 0.2220 ± 0.0128 stat ± 0.0050stat ± 0.0037 th, a02 = -0.0432 ± 0.0086stat ± 0.0034syst ± 0.0028th. Combination of this result with the other NA48/2 measurement obtained in the study of K± → Π0Π0π± decays brings an improved determination of a00 and the first precise experimental measurement of a02, providing a stringent test of Chiral Perturbation Theory predictions and lattice QCD calculations. Using constraints based on analyticity and chiral symmetry, even more precise values are obtained: a00 = 0.2196 ± 0.0028 stat ± 0.0020stat and a02 = -0.0444 ± 0.0007stat ± 0.0005syst ± 0.0008chPT.
ASJC Scopus subject areas
- Engineering (miscellaneous)
- Physics and Astronomy (miscellaneous)