Study of dimuon production in photon-photon collisions and measurement of QED photon structure functions at LEP

Muon pair production in the process e(+)e(-) --> e(+)e(-)mu (+)mu (-) is studied using the data taken at LEP1 (roots similar or equal to m(Z)) with the DELPHI detector during the years 1992-1995. The corresponding integrated luminosity is 138.5 pb(-1). The QED predictions have been tested over the whole Q(2) range accessible at LEP1 (from several GeV2/c(4) to several hundred GeV2/c(4)) by comparing experimental distributions with distributions resulting from Monte Carlo simulations using various generators. Selected events are used to extract the leptonic photon structure function F-2(gamma). Azimuthal correlations are used to obtain information on additional structure functions, F-A(gamma) and F-B(gamma), which originate from interference terms of the scattering amplitudes. The measured ratios F-A(gamma)/F-2(gamma) and F-B(gamma)/F-2(gamma) are significantly different from zero and consistent with QED predictions.