Article

# Revisiting parton evolution and the large-x limit

LPTHE, Universities of Paris-VI and VII and CNRS, Paris, France; University of Milano-Bicocca and INFN Sezione di Milano-Bicocca, Milan, Italy

Physics Letters B (Impact Factor: 4.57). 12/2005; DOI: 10.1016/j.physletb.2006.02.023 Source: arXiv

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**ABSTRACT:**We discuss recent results on the three-loop (next-to-next-to-leading order, NNLO) time-like splitting functions of QCD and the two-loop (NNLO) coefficient functions in one-particle inclusive e+e- annihilation. These results form the basis for extracting fragmentation functions for light and heavy flavors with NNLO accuracy that will be needed at the LHC and ILC. The two-loop calculations have been performed in Mellin space based on a new method, the main features of which we also describe briefly. Comment: Presented by A.M. at Loops and Legs in Quantum Field Theory, 23-28 April 2006, Eisenach, Germany09/2006; - [Show abstract] [Hide abstract]

**ABSTRACT:**The hadronic k{sub perpendicular}-spectrum inside a high-energy jet is determined including corrections of relative magnitude O(({sub s})) with respect to the Modified Leading Logarithmic Approximation (MLLA) in the limiting spectrum approximation (assuming an infrared cutoff Q={sub QCD}) and beyond (Q{sub QCD}). The results in the limiting spectrum approximation are found to be, after normalization, in impressive agreement with preliminary measurements by the CDF Collaboration, unlike what occurs at MLLA, pointing out small overall nonperturbative contributions. Within the same framework, 2-particle correlations inside a jet are also predicted at next-to-MLLA and compared to previous MLLA calculations.Physical review D: Particles and fields 01/2008; 78(1):014019-014019. - [Show abstract] [Hide abstract]

**ABSTRACT:**Anomalous dimensions of Wilson operators with large Lorentz spin scale logarithmically with the spin. Recent multi-loop QCD calculations of twist-two anomalous dimensions revealed the existence of interesting structure of the subleading corrections suppressed by powers of the Lorentz spin. We argue that this structure is a manifestation of the ‘self-tuning’ property of the multi-loop anomalous dimensions—in a conformal gauge theory, the anomalous dimension of Wilson operators is a function of their conformal spin which is modified in higher loops by an amount proportional to the anomalous dimension. Making use of the parity property of this function and incorporating the beta-function contribution, we demonstrate the existence of (infinite number of) relations between subleading corrections to the twist-two anomalous dimensions in QCD and its supersymmetric extensions. They imply that the subleading corrections to the anomalous dimensions suppressed by odd powers of the conformal spin can be expressed in terms of the lower-loops corrections suppressed by smaller even powers of the spin. We show that these relations hold true in QCD to all loops in the large β0 limit. In the N=4 SYM theory, we employ the AdS/CFT correspondence to argue that the same relations survive in the strong coupling regime for higher-twist scalar operators dual to a folded string rotating on the AdS3×S1.Nuclear Physics B 01/2007; · 4.33 Impact Factor

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