2 00 4 A New 5 Flavour NLO Analysis and Parametrizations of Parton Distributions of the Real Photon

New, radiatively generated, NLO quark (u, d, s, c, b) and gluon densities in a real, unpolarized photon are presented. We perform three global fits, based on the NLO DGLAP evolution equations for Q 2 > 1 GeV 2 , to all the available structure function F γ 2 (x, Q 2) data. As in our previous LO analysis we utilize two theoretical approaches. Two models, denoted as FFNS CJK 1 & 2 NLO, adopt the so-called Fixed Flavour-Number Scheme for calculation of the heavy-quark contributions to F γ 2 (x, Q 2), the CJK NLO model applies the ACOT(χ) scheme. We examine the results of our fits by a comparison with the LEP data for the Q 2 dependence of the F γ 2 , averaged over various x-regions, and the F γ 2,c. Grid parametrizations of the parton densities for all fits are provided.