Leading Isgur-Wise form factor of Lambda(b) -> Lambda(c1) transition usingQCD sum rules

The leading Isgur-Wise form factor xi (y) parametrizing the semileptonic tr ansitions Lambda (b) --> Lambda (1/2)(cl)l<(<nu>)over bar> and Lambdab --> Lambda (3/2)(cl)l<(<nu>)over bar> is calculated by using the QCD sum rules in the framework of heavy quark effective theory, where Lambda (1/2)(cl) an d Lambda (3/2)(cl) is the orbitaIly excited charmed baryon doublet with J(P ) = (1(-)/2, 3(-)/2). The interpolating currents with transverse covariant derivative are adopted for Lambda (1/2)(cl) and Lambda (3/2)(cl) in the ana lysis. The slope parameter rho (2) in linear approximation of the Isgur-Wis e function is obtained to be rho (2) = 2.01, and the interception to be xi (1) = 0.29. The decay branching ratios are estimated. (C) 2001 Published by Elsevier Science B.V.