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

Wang, Yu-Ming (Fakultät für Physik, Universität Wien, Boltzmanngasse 5, 1090, Vienna, Austria) (Physik Department T31, Technische Universität München, James-Franck-Straße 1, D-85748, Garching, Germany) ; Shen, Yue-Long (College of Information Science and Engineering, Ocean University of China, Songling Road 238, Qingdao, Shandong, 266100, P.R. China)

02 March 2016

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 O α s $$ \mathcal{O}\left({\alpha}_s\right) $$ 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.

Published in: JHEP 1602 (2016) 179
Published by: Springer/SISSA
DOI: 10.1007/JHEP02(2016)179
arXiv: 1511.09036
License: CC-BY-4.0

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