MEASUREMENTS OF Ke4 AND K± 7r°7r°7r±DECAYS

摘要

The NA48/2 experiment at the CERN SPS collected in 2003 and 2004 large samples of the decays K± e±ve (Ke4— K± wo 7ro e± ue ( Keozo) and K± --+ 7C° ° . From the Ke4 — form factors and from the cusp in the 40 distribution of the K± oiro..± events, the 7r7r scattering lengths ag and .3 could be extracted. This measurement is a fundamental test of Chiral Perturbation Theory (xPT). The branching fraction and form factors of the Ke4 decay were precisely measured, using a much larger data sample than in previous experiments.