[en] This report summarizes experimental results obtained by the CELLO, JADE, PLUTO and TASSO collaborations on the following topics: the structure function of the photon; hard scattering and jet production and exclusive hadron pair production. (orig.)

[en] After a brief general introduction into two-photon scattering processes the status of two-photon physics as of the beginning of this workshop is reported. Emphasis is given to those subjects which should get more attention in the future. (orig.)

[en] In this talk experimental results on the non-resonant production of hadrons in soft ßß scattering are reviewed: The measured cross sections for the production of hadron pairs by two photons are compared to theoretical predictions (QCD calculations above about 2 GeV). Analyses of four pion final states are reported, including an angular correlation analysis of p₀p₀, first results on p⁺p^- production and the observation of a narrow structure in the four pion mass spectrum near 2.1 GeV. The experimental results on the total hadronic cross section for photon-photon scattering are critically discussed. (orig.)

[en] The current experimental knowledge on the two-photon couplings of scalar and tensor mesons is reviewed. Special attention is paid to the conjecture that the missing scalar quark model states may be hidden under the tensor states. (orig.)

[en] Two selected topics on two photon physics from the TASSO experiment are presented: the two photon production of proton-antiproton pairs and the two photon production of rho⁰rho⁰. The reaction γγ → panti p has been measured in the panti p mass range from 2.0 GeV to 3.0 GeV. The data are compared to predictions from perturbative QCD. A new analysis of the reaction γγ → anti p⁰anti p⁰ → 2π⁺2π^- has been performed for 1.2 GeV <= M₄sub(π) <= 2.0 GeV. The cross section is flat from 1.2 to 1.7 GeV and then drops off towards higher energies, with no obvious resonance structure around 1.5 GeV. An analysis of the angular correlations of the four pions excludes dominant contributions from resonances with Jsup(P) = 0^- or 2^-. The large cross section cannot be explained by known resonances. (orig.)

[en] In this talk some recent results on two-photon scattering processes from DESY are presented, including results on the production of the charmonium state etasub(c)(2980), on the exclusive production of proton-antiproton pairs, on jet formation by two quasi-real photons, and on Λsub(anti Manti S) determinations from the structure function of the photon. (orig.)

[en] The following recent results from e⁺e^- experiments are presented: Particle searches: The search for the top quark at PETRA and the observation of B-mesons at CESR. The latest results from PETRA and PEP experiments on weak neutral current effects. The status of the experimental determination of the strong coupling constant αsub(s) and a high statistics measurement of the gluon spin. Results on the fragmentation of quark and gluon jets, such as: the particle composition of jets, heavy quark fragmentation (Dsup(*) production) and differences between quark and gluon jets. Two-photon physics: results on the structure function of the photon. (orig.)

[en] This report reviews the experimental status of two-photon physics and discusses to what extent the theoretical predictions for two-photon reactions have been corroborated by experiment. (orig.)

[en] A detailed analysis of the hadronic final state in the decay τ → a₁ν_τ yields the currently most significant determinations of the a₁ resonance parameters. Reported results include the mass and width of the a₁ resonance, the D/S ratio for the ρπ intermediate state, the τ decay branching ratio into three charged pions and an update of the parity violating asymmetry parameter γ_AV. (orig.)

[en] The current knowledge on the decays of τ leptons into hadrons is summarized. The decays are discussed in terms of the hadronic weak currents and compared to theoretical predictions. The presented topics include: the QCD analysis of the hadronic decay width and the determination of the strong coupling constant at the τ mass scale, analyses of the pion form factor and the a₁(1260) resonance parameters, improved limits on second class currents, analyses of the Lorentz structure of the τ - ν_τ vertex and limits on the τ neutrino mass. Also discussed is the (still existing) deficit in the exclusive τ decay branching ratios. (author). 34 refs., 11 figs., 3 tabs