Experimental Results on Two-Photon Physics from LEP

Abstract

Abstract. This review covers selected results from the LEP experiments on the structure of quasi-real and virtual photons. The topics discussed are the total hadronic cross-section for photon-photon scattering, hadron production, jet cross-sections, heavy quark production for photon-photon scattering, photon structure functions, and crosssections for the exchange of two virtual photons.

The photon structure from deep inelastic electron–photon scattering

“…For the important details, which are not given here the reader is referred to the most recent publications and to summaries of the LEP and HERA results, which can be found in Refs. [185][186][187][188].…”

Deep inelastic scattering, diffraction and all that

“…This implies an inhomogeneous term in the evolution equations and leads to a logarithmic enhancement in F γ(P 2 ) 2,L (x, Q 2 ) which means positive scaling violations for all values of x (Fig. 16) [26]. The 'resolved' component obeys the same evolution equations typical of the lepton-hadron interactions.…”

“…In recent years several sets of parton distributions for real and virtual photons have been proposed [27,28]. For virtual photons, different approaches have been followed in LO y NLO global fits to the available LEP data (Figure 17) [26]. LEP data constraint reasonably well the quark distributions in the photon, however, in order to constrain the gluon densitiy it is much more suitable to analyze dijet production processes in e + p collisions as measured at HERA.…”