[en] Two topics in e⁺e^-→τ⁺τ^- measured with the OPAL experiment at LEP are presented. The first is a measurement of α_s obtained from R_τ, the ratio of hadronic to leptonic decay fractions, and its extrapolation to Q²=m_Z². The method and associated errors are discussed and the result is compared to α_s determinations using various techniques. Second, the same reaction is used to perform a test of CP-invariance in this neutral current process. The obtained null result is used to place an upper limit on the weak dipole moment of the τ lepton. (orig.)

[en] The status of experimental investigations of high p/sub T/ phenomena and jet production in photon-photon collisions is reviewed. Taking the challenging questions on hard scattering processes in γγ reactions as a guide, the experimental approach to these questions is summarized. Results from the PETRA experiments CELLO, JADE, PLUTO, and TASSO are presented including preliminary results on the Q²-dependence of jet cross sections. Experimental limitations and background problems are discussed. 36 references

[en] Recent results on radiative decays of the J/PSI, obtained by the SPEAR detectors Mark III and Crystal Ball and the DCI detector DM2 at Orsay, are presented. The status of the glueball candidates theta(1690), iota(1460), and xi(220), and the decays J/PHI → γ Vector Vector are reviewed. A coupled channel analysis of iota(1460) decays to K anti Kπ, rho rho, ωω, and γrho is presented which may help to understand the pseudoscalar sector in radiative J/PHI decays. 42 refs., 16 figs

[en] The spectrum of the light q anti q states is still not satisfactorily understood. In addition, the predicted existence of states not being bound systems of two valence quarks is unsettled despite a large experimental effort during the last decade. In order to move a significant step forward in addressing these issues an improvement by several orders of magnitude with respect to statistics as well as systematics is needed. It is shown that a dedicated high-luminosity e⁺e^--collider operating a 3-4 GeV centre of mass energy is capable to challenge this demand. The issue is addressed by analyzing radiative and hadronic decays of the J/ψ as well as photon-photon reactions with the same detector. (orig.)

[en] Selected topics on radiative decays of the J/psi from MARK III at SPEAR are presented. These topics include the decay J/psi → γK anti K where the final state resonances f'(1515), theta(1700) and xi(2200) have been analyzed. The decay J/psi → (γ vector vector) is presented in three final states, J/psi → γ phi phi, γ rho rho and γωω, providing the first measurement of the eta/sub c/ spin-parity (in γ phi phi) and evidence for structures (in γ rho rho and γωω) near 1.7 GeV. 24 references

[en] The physics potential and the current status of the Tau-charm Factory are presented. The highlights of the programme of tau physics, on chermed meson physics, and on charmonium physics including kight meson and glueball spectroscopy from J/ψ decays are discussed. The design of the machine, the Tau-Charm detector and the present status of the proposal are also presented

[en] The reaction τ → 3h(π²)ν_τ as measured by OPAL has been used to (a) determine the respective branching fractions and (b) to extract information on the nature of the hadronic current mediating the decay. Two methods have been employed for the latter. One is a fit to the dalitz plot variables of the three hadron (pion) final state using two recent models. The second approach uses a model independent description of the hadronic final state resulting in a measurement of four hadronic structure functions characterizing the decay. (orig.)

[en] A Design and some R and D work on components of the forward elements of the τ-charm detector are presented. (orig.)

[en] The spectrum of the light qq states is still not satisfactorily understood. In addition, the predicted existence of states not being bound systems of two valence quarks is unsettled despite a large experimental effort during the last decade. In order to move a significant step forward in addressing these issues an improvement by several orders of magnitude with respect to statistics as well as systematics is needed. It is shown that a dedicated high-luminosity e⁺e^- -collider operating at 3-4 GeV centre of mass energy is capable to challenge this demand. The issue is addressed by analyzing radiative and hadronic decays of the J/ψ as well as photon-photon reactions with the same detector. (author). 23 refs., 9 figs., 7 tabs

[en] Tests of CP invariance in the reaction e⁺e^-→τ⁺τ^- on the Z⁰ and measurements of the weak and electric (magnetic) dipole moments of the τ lepton are reviewed. The relative importance of the measurements in terms of several models are discussed. Averaging the present LEP measurements, upper limits on the real and imaginary parts of the weak dipole moment of the τ lepton of vertical stroke Re(d_τ^w(M_Z²)) vertical stroke <3.6.10^-18 e cm and vertical stroke Im(d_τ^w(M_Z²)) vertical stroke <1.1.10^-17 e cm with 95% c.l. are obtained. Results on measurements on the weak magnetic moment and the anomalous (electric) magnetic moment are also reported. (orig.)