Perturbative corrections to Λ _b → Λ form factors from QCD light-cone sum rules

Abstract: We compute radiative corrections to Λ _b → Λ from factors, at next-to-leading logarithmic accuracy, from QCD light-cone sum rules with Λ _b-baryon distribution amplitudes. Employing the diagrammatic approach factorization of the vacuum-to-Λ _b-baryon correlation function is justified at leading power in Λ/m _b, with the aid of the method of regions. Hard functions entering the factorization formulae are identical to the corresponding matching coefficients of heavy-to-light currents from QCD onto soft-collinear effective theory. The universal jet function from integrating out the hard-collinear fluctuations exhibits richer structures compared with the one involved in the factorization expressions of the vacuum-to-B-meson correlation function. Based upon the QCD resummation improved sum rules we observe that the perturbative corrections at (Formula presented.) shift the Λ _b → Λ from factors at large recoil significantly and the dominant contribution originates from the next-to-leading order jet function instead of the hard coefficient functions. Having at hand the sum rule predictions for the Λ _b → Λ from factors we further investigate several decay observables in the electro-weak penguin Λ _b → Λ ℓ ⁺ℓ ⁻ transitions in the factorization limit (i.e., ignoring the “non-factorizable” hadronic effects which cannot be expressed in terms of the Λ _b → Λ from factors), including the invariant mass distribution of the lepton pair, the forward-backward asymmetry in the dilepton system and the longitudinal polarization fraction of the leptonic sector.