Abstract:

The charged particle multiplicity distribution for e⁺e^- annihilations at s = 29 GeV has been measured using the High Resolution Spectrometer at PEP. The multiplicity distribution, expressed as a function of the mean, shows KNO scaling when compared to e⁺e^- data at other energies. Multiplicity distributions for particles selected in different central rapidity spans are presented. All of these are well presented by the Negative binomial distribution. As the rapidity span is narrowed, the distributions become broader and approach a constant value of the parameter k. © 1986.

Abstract:

Results are reported on a high statistics study of Bhabha scattering at 29 GeV in the polar angle region, |cos θ| < 0.55. The data are consistent with the standard model, and measure vector and axial-vector coupling constants of gv2 = 0.03 ± 0.09 and ga2 = 0.46±0.14. Limits on the QED-cutoff parameters are Λ+ > 154 GeV and Λ- > 220 GeV. Lower limits on scale parameters of composite models are in the range 0.9-2.8 TeV. The partial width of a hypothetical spin-zero boson decaying to e+e- has an upper limit which varies from 6 to 57 MeV corresponding to a boson mass in the range 45-80 GeV/c2. © 1986.

Abstract:

The ratio of differential cross sections for the reactions e⁺e^- → γγ and e⁺e^- → e⁺e^- is measured at s = 29 GeV in the central polar angle region, |cos θ| < 0.55, and compared to the same ratio calculated by QED to order α³. The ratio of these ratios, integrated over this angular region, is 1.007±0.009±0.008, demonstrating excellent agreement between theory and experiment. The 95% confidence limits on the QED cut-off parameters for the γγ final state are Λ+ > 59 GeV and Λ- > 59 GeV. © 1986.

Abstract:

The UA2 experiment, running at the CERN SPS {Mathematical expression} Collider, has performed a study of events containing three hard jets in the final state. The angular distributions of the three jets show evidence for gluon bremsstrahlung, in good agreement with a QCD model to leading order in the strong coupling constant αs. The yield of three-jet events relative to that of two-jet events provides a measure of the strong coupling constant: ;3K3/K2=0.23±0.01±0.04, where K2 and K3 represent the contributions arising from higher order corrections in α3 to the two- and three-jet exclusive cross-sections. A detailed discussion of the systematic and theoretical uncertainties is given. © 1986 Springer-Verlag.

Abstract:

A study of W± and Z0 properties has been performed using the UA2 detector at the {Mathematical expression} collider. The data correspond to a total integrated luminosity of 142 nb-1 at {Mathematical expression}=546 GeV, and of 310 nb-1 at {Mathematical expression}=630 GeV. The experimental results are compared with the predictions of the Standard Model of the unified electroweak theory. © 1986 Springer-Verlag.