New NLO Parametrizations of the Parton Distributions in Real Photons

37 pages, 23 Postscript figuresInternational audienceWe present new NLO sets of parton distributions in real photons based on a scheme invariant definition of the non-perturbative input. We compare the theoretical predictions with LEP data and a best fit allows us to constrain the parameters of the distributions. The shape of the gluon distribution is poorly constrained and we consider the possibility to measure it in photoproduction experiments. Three parametrizations which aim to take into account the scattering of LEP data are proposed. They are compared to the AFG parametrization