ASSESSING QCD IN DEEP-INELASTIC ey SCATTERING

We consider hadron production in deep inelastic scattering of electrons on photons. (i) Exploiting the leading order QCD corrections due to gluon bremsstrahlung we find that the photon structure functions rapidly approach their asymptotic form which can be calculated in QCD. (ii) Replacing QCD by a theory with fixed quark-gluon coupling constant [scalar or Abelian gluonsl gives dramatic changes: for Bjorken x away from 0, the asymptotic form of the structure function is scale-invariant, with a shape quite unlike the QCD shape, and the structure function diverges for x = 0. (iii) The pointlike component of the photon gives final state jets emerging at large angles to the axis of the real + virtual photon, in contrast to the hadronic component of the photon. Submitted to Nuclear Physics B Work supported in part by the Department of Energy under contract DE-AC03-76SF00515. -f Present Address: NORDITA, Blegdamsvej 17, DK-2100 Copenhagen. § Kade Fellow, on leave from Technische Hochschule Aachen.