Measurement of the KL meson lifetime with the KLOE detector

We present a measurement of the K-L lifetime using the KLOE detector. From a sample of similar to 4 x 10(8) KSKL pairs following the reaction e(+)e(-) -> Phi -> KSKL we select similar to 15 x 10(6) K-L pi(0)pi(0)pi(0) decays tagged by K-S -> pi(+)pi(-) events. From a fit of the proper time distribution we find tau(L) = (50.92 +/- 0.17(stat) +/- 0.25(syst)) ns. This is the most precise measurement of the KL lifetime performed to date. (c) 2005 Elsevier B.V. All rights reserved.