High statistics measurement of Ke4 decay properties -: art. no. 072004

We report experimental details and results of a new measurement of the decay K+-->pi(+)pi(-)e(+)nu(e)(K-e4). A sample of more than 400,000 K-e4 events with low background has been collected by Experiment 865 at the Brookhaven Alternate Gradient Synchrotron. From these data, the branching ratio (4.11+/-0.01+/-0.11)x10(-5) and the pipi invariant mass dependence of the form factors F, G, and H of the weak hadronic current as well as the phase shift difference delta(0)(0)-delta(1)(1) for pipi scattering were extracted. Using constraints based on analyticity and chiral symmetry, a new value with considerably improved accuracy for the s-wave pipi scattering length a(0)(0) has been obtained also: a(0)(0)=0.216+/-0.013 (stat)+/-0.002 (syst)+/-0.002 (theor).