We report results from the analysis of the K± → π + π −e± ν (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 the a00 and a20, the I = 0 and I = 2 S-wave ππ scattering lengths. Combination of this result with the other NA48/2 measurement obtained in the study of decays brings an improved determination of a00 and the first precise experimental measurement of a20, 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.
Precise tests of low energy QCD from Ke4 decay properties
BALDINI, Wander;COTTA RAMUSINO, Angelo;DALPIAZ, Pietro;FIORINI, Massimiliano;GIANOLI, Alberto;PETRUCCI, Ferruccio Carlo;SAVRIE', Mauro;
2010
Abstract
We report results from the analysis of the K± → π + π −e± ν (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 the a00 and a20, the I = 0 and I = 2 S-wave ππ scattering lengths. Combination of this result with the other NA48/2 measurement obtained in the study of decays brings an improved determination of a00 and the first precise experimental measurement of a20, 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.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
