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

摘要

Muon pair production in the process (e^+e^- o 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^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.