[en] The MARK-J experiment, built and operated by a group of fifty-six physicists from Aachen, DESY, MIT, NIKHEF, and Peking, occupies the southwest intersection at PETRA. The primary design goal of the experiment is to measure the forward-backward charge asymmetry in muon production which is expected from the interference of weak and electromagnetic interactions, but it is also well suited to investigate other physics processes. (orig./HSI)

[en] A study of hadron production in e⁺e^- collisions at the highest PETRA energies reached so far is reported. Production of a new quark flavor was sought at cms energies of 33, 35, and 35.8 GeV. The measured values of the total cross section, the thrust distributions, and the study of inclusive muon production show no evidence for the production of a new charge 2/3e quark near threshold. In addition, during an energy scan zn the region 29.9 less than or equal to √s less than or equal to 31.6 GeV, no hadron resonance indicting the existence of a bound state composed of charge 2/3e quarks was bound. 4 figures, 1 table

[en] A new drift chamber suitable for large area detectors is compared to a multiwire field shaped module. The behavior of both is understood from their electrostatic field and the predicted behavior for inclined tracks correctly verified by measurement. (Auth.)

[en] We have measured at √s=62 GeV, at the CERN Intersecting Storage Rings, the associated charged hadrons with massive μ pairs, employing a vertex detector of approx. equal to 4 π coverage. The experiment has provided the first data on hadron multiplicity, angular distributions, and correlations in lepton pair events at ISR energies. The average associated charged multiplicity [nsub(ch)] is found to increase as the invariant mass of the hadronic system Msub(h) increases, similarly to the observed √s dependence in e⁺e^- annihilation into hadrons at high energies. The multiplicity also increases with psub(T) in the hemisphere opposite to the transverse momentum psub(T) of the dimuon. Small clusters appear to be produced, whose correlation with the μ-pair can be explained in a simple Monte Carlo model incorporating the production of a weakly collimated jet of low multiplicity, recoiling against the dimuon. (orig.)

[en] This report reviews the experimental investigation of high energy e⁺e^- interactions by the MARK J collaboration at PETRA, the electron-positron colliding beam accelerator at DESY in Hamburg, Germany. The phyiscs objectives include studies of several purely electromagnetic processes and hadronic final states, which further our knowledge of the nature of the fundamental constituents and of their strong, electromagnetic and weak interactions. Before discussing the physics results, the main features and the principal components of the MARK J detector are discussed in terms of design, function, and performance. Several aspects of the on-line data collection and the off-line analysis are also outlined. Results are presented on tests of quantum electrodynamics using e⁺e^- → μ⁺μ^- and tau⁺tau^-, on the measurement of R, the ratio of the hadronic to the point-like muon pair cross section, on the search for new quark flavors, on the discovery of three jet events arising from the radiation of hard noncollinear gluons as predicted by quantum chromodynamics, and on the determination of the strong coupling constant αsub(s). (orig.)

[en] We have used our measurements of final states from e⁺e^- containing an isolated muon and a hadronic or electron shower to search for new spin 0 charged particles. We exclude (95% CL) a supersymmetric partner of the tau with a mass less than 14 GeV/c². We obtain upper limits on the branching ratio to tauνsub(tau) for charged Higgs particles or technipions with masses up to 14 GeV/c². This disagrees with some technicolor model predictions. (orig.)

[en] We have performed a high statistics measurement of the production rate and the energy flow pattern of hadron events between √s = 33 and 36.7 GeV. The data show no evidence for the production of a new quark with charge 2/3e. Planar events in e⁺e^-→ hadrons are shown to have three well sepparated jets. The production rate and the shape of three-jet events are compared with many models and we find that only the QCD model can explain the data. (orig.)

[en] By combininb results from the MARK-J at PETRA on Bhabha scattering, μ⁺μ^- and tau⁺tau^- production with recent world data from neutrino-electron scattering experiments, we determine unique values for the leptonic weak neutral current coupling constants gsub(V) and gsub(A) in the framework of electroweak models containing a single Z⁰. In contrast to previous analyses, we only use data from purely leptonic interactions, and therefore avoid the inherent uncertainties resulting from the use of hadronic targets. From the MARK-J data alone in the context of the standard SU(2) x U(1) model of Glashow, Weinberg and Salam, we find sin²THETAsub(W) = 0.24 +- 0.11. (orig.)

[en] As part of an effort to upgrade the L3 detector for LEP2 we have performed measurements on an L3 muon chamber using a 100 MHz FADC system and cosmic rays. By studying the time dependence of the pulse shape distribution of small-slope (<0.12) minimum ionizing tracks we found significant induction-crosstalk. Correcting for these effects results in about a factor of 1.6 improvement in spatial resolution. Similar improvements may be expected in other multiwire drift chamber systems. ((orig.))

[en] We report the results of a study of the mechanism of inclusive dimuon production from the reaction p+p→μ⁺μ^-+X at the CERN intersecting storage rings. The present experiment was done at the center-of-mass energies √s = 62 and 44 GeV and in the dimuon pair invariant-mass region m = 3-25 GeV. The dependence on the Feynman variable x has been measured. The average transverse momentum is found to increase with √s and with mass and reaches < p/sub T/>approx. =1.9 GeV, compatible with predictions from quantum-chromodynamic gluon processes