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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 (sqrt(s) \simeq 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 GeV^2/c^4 to several hundred GeV^2/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^γ. Azimuthal correlations are used to obtain information on additional structure functions, F_A^γand F_B^γ, which originate from interference terms of the scattering amplitudes. The measured ratios F_A^γ/F_2^γand F_B^γ/F_2^γare significantly different from zero and consistent with QED predictions.