Parton Distributions in the Photon

Abstract

We discuss in detail the photon structure function beyond the leading logarithm approximation. Of special concern is the factorization scheme and the hadronic input; we show how to naturally absorb large terms due to the MSbar factorization scheme in a modified hadronic component. The effect of the charm quark mass threshold is also discussed in relation to the phenomenology. A comparison with data shows that the modified hadronic component can be reasonably described by a VDM-type input.

Comments: 26 pages, postscript files appended to the TEX file contain fig. 1,2,3, 5,6,7. Missing figures are sent on request , ENSLAPP-A-435-93-a and LPTHE Orsay 93-37-a