Λb→p,Λtransition form factors from QCD light-cone sum rules

Abstract

Light-cone sum rules for the Lambda(b) -> p, Lambda transition form factors are derived from the correlation functions expanded by the twist of the distribution amplitudes of the Lambda(b) baryon. In terms of the Lambda(b) three-quark distribution amplitude models constrained by the QCD theory, we calculate the form factors at small momentum transfers and compare the results with those estimated in the conventional light-cone sum rules (LCSR) and perturbative QCD approaches. Our results indicate that the two different versions of sum rules can lead to the consistent numbers of form factors responsible for Lambda(b) -> p transition. The Lambda(b) -> Lambda transition form factors from LCSR with the asymptotic Lambda baryon distribution amplitudes are found to be almost 1 order larger than those obtained in the Lambda(b)-baryon LCSR, implying that the preasymptotic corrections to the baryonic distribution amplitudes are of great importance. Moreover, the SU(3) symmetry breaking effects between the form factors f(1)(Lambda b -> p) and f(1)(Lambda b ->Lambda) are computed as 28(-8)(+14)% in the framework of Lambda(b)-baryon LCSR.