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.