PHYSICS OF ELEMENTARY PARTICLES AND ATOMIC NUCLEI . EXPERIMENT Two - Photon Interactions at LEP

INTRODUCTION This work is the overview of experimental results on the investigation of photon interactions obtained at LEP. The generalized diagram of the reaction (e + e – e + e – + X) is shown in Fig. 1 [1]. Incident electrons 1 emit virtual photons which due to the uncertainty principle fluctuate to some intermediate state: / pair or quark–gluon system. The two-photon interaction can be represented, for example, as scattering of one of the photons off the lepton of the intermediate state formed by the other photon. The diagrams of γγ interactions will be given below. The following kinematical variables (Fig. 1) are used for a description of γγ interactions: (i) p i is the incident electron four-momentum; E beam is the energy, and s is the squared total energy of electrons in the center-of-mass system; (ii) , are the scattered electron four-momentum and polar angle; (iii) q i is the virtual photon four-momentum. Here