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arXiv · 0807.1238

Towards the NNLO evolution of polarised parton distributions

A. Vogt·S. Moch·M. Rogal·J. A. M. Vermaseren
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Abstract

We report on the first calculation of the structure function g_1 in polarised deep-inelastic scattering to the third order in massless perturbative QCD. The calculation follows the dispersive approach already used for the corresponding unpolarised cases of F_2,L, but additionally involves higher tensor integrals and the Dirac matrix gamma_5 in D unequal 4 dimensions. Our results confirm all known two-loop expressions including the coefficient functions of Zijlstra and van Neerven not independently verified before. At three loops we extract the helicity-difference next-to-next-to-leading order (NNLO) quark-quark and gluon-quark splitting functions Delta P_qq and Delta P_qg. The results exhibit interesting features concerning sum rules and the momentum-fraction limits x to 1 and x to 0.

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A. Vogt, S. Moch, M. Rogal, J. A. M. Vermaseren. 2008-07-08. Towards the NNLO evolution of polarised parton distributions. https://doi.org/10.1016/j.nuclphysbps.2008.09.097

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