Measurement of the form-factor slopes for the decay K-L -> pi(+/-)e(+/-)nu with the KLOE detector

We present a measurement of the K-pi vector current form-factor parameters for the decay K-L -> pi(+/-)e(-/+)nu. We use 328 pb(-1) of data collected in 2001 and 2002, corresponding to similar to 2 million K-e3 events. Measurements of semileptonic form factors provide information about the dynamics of the strong interaction and are necessary for evaluation of the phase-space integral I-K(e) needed to measure the CKM matrix element |V-us| for K-L -> pi(+/-)e(-/+)nu decays. Our result is lambda(+) = (28.6 +/- 0.5 +/- 0.4) x 10(-3) for a linear fit, and lambda'(+) = (25.5 +/- 1.5 +/- 1.0) x 10(-3), (1.4 +/- 0.7 +/- 0.4) x 10(-3) for a quadratic fit. (c) 2006 Elsevier B.V. All rights reserved.