Measurement of the Form-Factor Slopes for the Decay KLe3 with the KLOE Detector

We present a measurement of the K-pi vector current form-factor parameters for the Ke3 decay. We use 328 pb$^{-1}$ of data collected in 2001 and 2002, corresponding to about 2 million Ke3 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 Ie_K needed to measure the CKM matrix element Vus for Ke3 decays. Our result is $l=(28.6\pm0.5\pm0.4)10^{-3}$ for a linear fit, and $l'=(25.5\pm1.5\pm1.0)10^{-3}$, $l''=(1.4\pm0.7\pm0.4)10^{-3}$ for a quadratic fit.