Measurement of the branching ratio of the decay KL -> pi+- e-+ nu and extraction of the CKM parameter abs(Vus)

We present a new measurement of the branching ratio R of the decay K-L --> pi(+/-) e(-/+)v, denoted as K(e)3, relative to all charged K-L decays with two tracks, based on data taken with the NA48 detector at the CERN SPS. We measure R = 0.4978 +/- 0.0035. From this we derive the K(e)3 branching fraction and the weak coupling parameter \V-us\ in the CKM matrix. We obtain \V-us\ f(+) (0) = 0.2146 +/- 0.0016, where f(+) (0) is the vector form factor in the K(e)3 decay. (C) 2004 Published by Elsevier B.V.