New Parton Distribution Functions for the Photon

Abstract

We present new improved parton distributions for the photon. We fit all available data on the photon structure function, F γ 2 (x,Q2), with Q 2 ≥ 3 GeV 2, in order to determine the quark distributions. We also pay particular attention to the gluon distribution in the photon, g γ (x,Q 2), which has been poorly constrained in earlier analyses which only include structure function data. We use large pT jet production in γγ collisions from TRISTAN to constrain g γ. We also see what information can be gleaned from γp collisions at HERA on g γ and on the quark distributions at large x, where there are no structure function data. We review future prospects of elucidating the parton distributions of the photon. Typeset using REVTEX 1 I.