Heavy-to-light baryonic form factors at large recoil

We analyze heavy-to-light baryonic form factors at large recoil and derive the scaling behavior of these form factors in the heavy quark limit. It is shown that only one universal form factor is needed to parameterize Lambda(b) -> p and Lambda(b) -> Lambda matrix elements in the large recoil limit of light baryons, while hadronic matrix elements of Lambda(b) -> Sigma transition vanish in the large energy limit of Sigma baryon due to the space-time parity symmetry. The scaling law of the soft form factor.(P'.v), P' and v being the momentum of nucleon and the velocity of Lambda(b) baryon, responsible for Lambda(b) -> p transitions is also derived using the nucleon distribution amplitudes in leading conformal spin. In particular, we verify that this scaling behavior is in full agreement with that from light-cone sum rule approach in the heavy-quark limit. With these form factors, we further investigate the Lambda baryon polarization asymmetry alpha in Lambda(b) -> Lambda(gamma) and the forward-backward asymmetry A(FB) in Lambda(b) -> Lambda l(+)l(-). Both two observables (alpha and A(FB)) are independent of hadronic form factors in leading power of 1/m(b) and in leading order of alpha(s). We also extend the analysis of hadronic matrix elements for Omega(b) -> Omega transitions to rare Omega(b) -> Omega(gamma) and Omega(b) -> Omega l(+)l(-) decays and find that radiative Omega(b) -> Omega(gamma) decay is probably the most promising FCNC b -> s radiative baryonic decay channel. In addition, it is interesting to notice that the zero-point of forward-backward asymmetry of Omega(b) -> Omega l(+)l(-) is the same as the one for Lambda(b) -> Lambda l(+)l(-) to leading order accuracy provided that the form factors (zeta) over bar (i) (i = 3, 4, 5) are numerically as small as indicated from the quark model.