Dynamical next-to-next-to-leading order parton distributions and the perturbative stability ofFL(x,Q2)

Abstract

Recent measurements for ${F}_{2}(x,{Q}^{2})$ have been analyzed in terms of the ``dynamical'' and ``standard'' parton model approach at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of perturbative QCD. Having fixed the relevant NLO and NNLO parton distributions, we present the implications and predictions for the longitudinal structure function ${F}_{L}(x,{Q}^{2})$. It is shown that the previously noted extreme perturbative NNLO/NLO instability of ${F}_{L}(x,{Q}^{2})$ is an artifact of the commonly utilized ``standard'' gluon distributions. In particular it is demonstrated that using the appropriate---dynamically generated---parton distributions at NLO and NNLO, ${F}_{L}(x,{Q}^{2})$ turns out to be perturbatively rather stable already for ${Q}^{2}\ensuremath{\ge}\mathcal{O}(2--3\text{ }\text{ }{\mathrm{GeV}}^{2})$.