NNLO corrections to B -> X u l nu and the determination of |V ub| - High Energy Physics - PhenomenologyReport as inadecuate

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Abstract: We study the impact of next-to-next-to-leading order NNLO QCD correctionson partial decay rates in B -> X u l nu decays, at leading-order in the 1-m bexpansion for shape-function kinematics. These corrections are implementedwithin a modified form of the BLNP framework, which allows for arbitraryvariations of the jet scale mu i \sim 1.5 GeV. Our analysis includes a detailedcomparison between resummed and fixed-order perturbation theory, and betweenthe complete NNLO results and those obtained in the large-$\beta 0$approximation. For the default choice mu i=1.5 GeV used in current extractionsof |V ub| within the BLNP framework, the NNLO corrections induce significantdownward shifts in the central values of partial decay rates with cuts on thehadronic variable P +, the hadronic invariant mass, and the lepton energy. Atthe same time, perturbative uncertainties are reduced, especially those at thejet scale, which are the dominant ones at next-to-leading order NLO. Forhigher values of mu i and in fixed-order perturbation theory, the shiftsbetween NLO and NNLO are more moderate. We combine our new results with knownpower-suppressed terms in order to illustrate the implications of our analysison the determination of |V ub| from inclusive decays.

Author: C. Greub, M. Neubert, B.D. Pecjak

Source: https://arxiv.org/

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