MEASUREMENT OF THE PHOTON STRUCTURE-FUNCTION F2-GAMMA AT Q2 FROM 7 TO 70 (GEV/C)2

We have measured the processe + e −→e + e −+hadrons, where one of the scattered electrons was detected at large angles, withQ 2 ranging from 7 to 70 (VeV/c)2. The photon structure functionF 2 γ (x, Q2) was determined at an averageQ 2 of 23 (GeV/c)2. The measurements were compared to theoretical predictions of the Quark Parton Model and Quantum Chromodynamics. In both models a hadronic part was added. Within the errors the data are in agreement with the QPM using quark masses of 300 MeV/c2 for the light quarks. The data also agree with a QCD calculation including higher order corrections. A fit yielded a $$\Lambda _{\overline {MS} } $$ value of 140 −65 +190 MeV, where the errors include statistical and systematic uncertainties.