Regge residues from Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution

Abstract

We show that combining forward and backward evolution allows us to extract the residues of the triple-pole Pomeron and of the other singularities for $10<~{Q}^{2}<~1000{\mathrm{GeV}}^{2}.$ In this approach, the essential singularity generated by the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution is considered as a numerical approximation to a triple-pole Pomeron. The ${Q}^{2}$-dependent form factors, unknown in Regge theory, are predicted by the DGLAP equation, and lead to a fit to the experimental data with a ${\ensuremath{\chi}}^{2}/dof$ of 1.02. In our case, Regge theory applies at all values of ${Q}^{2}.$ The method used here gives two main results: first, the parton content of the Pomeron is given at large ${Q}^{2}$ by DGLAP evolution, and second, we can evaluate the uncertainties on the gluon distribution which prove to be large at small x and small ${Q}^{2}.$