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Abstract
| We study the effect of initial-state radiation in the double-tagged process ee to ee + hadrons by introducing the parton distribution functions associated with an electron, a positron, and a photon, which satisfy a set of Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equations. It is observed that the radiation effect is not essential in most of the kinematic range. This observation applies to the subprocess of two-photon collision via quark exchange and via onium scattering. The deviation of the LEP data from the prediction for quark exchange at large rapidity may be regarded as a sign of new mechanism, such as the Balitskii-Fadin-Kuraev-Lipatov mechanism. (15 refs). |