Large-x power laws of parton distributions remain inconclusive
Keywords:parton distribution functions, hadron structure, quark counting rules
Focusing on hadron scattering at large partonic momentum fractions x, we compare nonperturbative QCD predictions for the asymptotic behavior of DIS structure functions and parton distribution functions (PDFs) to the x and Q dependence of phenomenological PDFs. In the CT18 NNLO global QCD analysis, higher-order radiative contributions and functional mimicry of PDF parametrizations result in about one unit of uncertainty in the effective powers of (1 − x) falloff of nucleon PDFs. Similar uncertainties are present in the case of the pion PDF, an object of growing interest in phenomenology.
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