Note on the Slope Parameter of the Baryonic Λ_b to Λ_c Isgur-Wise Function

Using the framework of the Heavy Quark Effective Theory we have re-analyzed the Isgur-Wise function describing semileptonic Λ_b to Λ_c decays in the QCD sum rule approach. The slope parameter of the Isgur-Wise function is found to be ρ^2 = 1.35 \pm 0.12, which is consistent with an experimental measurement and a lattice calculation. To O(1/m_b,1/m_c) of the heavy quark expansion the integrated Λ_b decay width is used to extract the CKM matrix element V_{cb} for which we obtain a value of |V_{cb}| = 0.041 \pm 0.004 in excellent agreement with the value of |V_{cb}| determined from semileptonic B to D^* decays.

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