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Parton densities and structure functions at next-to-next-to-leading order and beyond

W. L. van Neerven·A. Vogt
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Abstract

We summarize recent results on the evolution of unpolarized parton densities and deep-inelastic structure functions in massless perturbative QCD. Due to last year's extension of the integer-moment calculations of the three-loop splitting functions, the NNLO evolution of the parton distributions can now be performed reliably at momentum fractions x >= 10^-4, facilitating a considerably improved theoretical accuracy of their extraction from data on deep-inelastic scattering. The NNLO corrections are not dominated, at relevant values of x, by their leading small-x terms. At large x the splitting-function series converges very rapidly, hence, employing results on the three-loop coefficient functions, the structure functions can be analysed at N^3LO for x > 10^-2. The resulting values for alpha_s do not significantly change beyond NNLO, their renormalization scale dependence reaches about +-1% at N^3LO.

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W. L. van Neerven, A. Vogt. 2001-07-17. Parton densities and structure functions at next-to-next-to-leading order and beyond. https://doi.org/10.1088/0954-3899%2F28%2F5%2F301

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