# Momentum Fractions carried by quarks and gluons in models of proton structure functions at small x

Published on Jun 30, 2017in International Journal of Modern Physics A1.153

· DOI :10.1142/S0217751X1750107X

Abstract

In this paper, we report an analysis of partial momentum fractions carried by quarks and gluons in six alternative phenomenological models of proton structure function valid in limited small x regions: xai ≤ x ≤ xbi, i = 1 to 6; the limits being determined by phenomenological range of validity in each model. Since the physics of small x is not completely understood at this point, we have considered both self-similarity-based as well as QCD-based models. The procedure by which one can determine the applicability ranges in x and Q2 of the models is presented. We find that while the self-similarity-based models with linear rise in Q2 has limited phenomenological ranges of validity, an improved version with linear rise in log Q2 has a wider phenomenological range. We then compare the partial momentum fractions in all the small x models. Our analysis implies that the role of small x sea quarks in calculating the second moments of parton distribution is minor one. We have also made a comprehensive comparison of all the phenomenological models considered to the available perturbative QCD, lattice QCD as well as Ads/QCD results.