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Next-to-next-to-leading order QCD corrections to the photon's parton structure

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

The next-to-next-to-leading order (NNLO) corrections in massless perturbative QCD are derived for the parton distributions of the photon and the deep inelastic structure functions F_1^gamma and F_2^gamma. We present the full photonic coefficient functions at order alpha alpha_s and calculate the first six even-integer moments of the corresponding O(alpha alpha_s^2) photon-quark and photon-gluon splitting functions together with the moments of the alpha alpha_s^2 coefficient functions which enter only beyond NNLO. These results are employed to construct parametrizations of the splitting functions which prove to be sufficiently accurate at least for momentum fractions x >= 0.05. We also present explicit expressions for the transformation from the MS_bar to the DIS_gamma factorization scheme and write down the solution of the evolution equations. The numerical impact of the NNLO corrections is discussed in both schemes.

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S. Moch, J. A. M. Vermaseren, A. Vogt. 2001-11-29. Next-to-next-to-leading order QCD corrections to the photon's parton structure. https://doi.org/10.1016/s0550-3213(01)00572-7

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