2008/10/06 by H. M. Asatrian, C. Greub, B. D. Pecjak
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph
paper · pdf · doi:10.1103/physrevd.78.114028
published as Phys.Rev.D78:114028,2008 · 17 pages, 1 figure
arxiv created 2008/10/06 · openalex publication_date 2008/12/22 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The inclusive decay B\ensuremath→Xu\ensuremathℓ\ensuremathν is of much interest because of its potential to constrain the CKM element |Vub|. Experimental cuts required to suppress charm background restrict measurements of this decay to the shape-function region, where the hadronic final state carries a large energy but only a moderate invariant mass. In this kinematic region, the differential decay distributions satisfy a factorization formula of the form H\ifmmode⋅\else\textperiodcentered\fiJ\ensuremath\bigotimesS, where S is the nonperturbative shape function, and the object H\ifmmode⋅\else\textperiodcentered\fiJ is a perturbatively calculable hard-scattering kernel. In this paper, we present the calculation of the hard function H at next-to-next-to-leading order (NNLO) in perturbation theory. Combined with the known NNLO result for the jet function J, this completes the perturbative part of the NNLO calculation for this process.