Hadronic Decays of the Upsilon Resonance - a Test of Quantum Chromodynamics.
We review some important theoretical predictions of quantum chromodynamics (QCD) for the (gamma)-direct hardonic decays and the continuum hadronic events in e('+)e(' -) annihilations. In particular, the differential cross sections for the (gamma)-direct decays and those for the continuum events are obtained from extensive theoretical work published recently. We show that these predictions, applied to the leading order QCD (gamma)-direct decays, lead to unique and nontrivial angular distributions of the major jet axis and the normal to the reconstructed event plane, measured with respect to the e('+)e('-) beam axis. These predictions are tested with events collected on the peak of the (gamma) resonance and continuum events at 10.49 GeV center of mass energy by using the CLEO detector at the Cornell Electron Storage Ring. A description of the apparatus is given in addition to a detailed review of the data reduction process. We present results of some important inclusive distributions for both the (gamma) -direct and continuum events. From a comparison with Monte Carlo studies we show that the event shape distributions for the (gamma)-direct decays, in addition to being in agreement with QCD, are qualitatively consistent with those obtained from an approximately equal admixture of continuum and phase space events. However, this is shown not to be the case for the angular measurements. We present a detailed study of the acceptance of the apparatus in the angular distributions and show that our measurements are justified. The angular distributions are fitted to a functional form proportional to (1 + (alpha)cos('2)(theta)). The results for (alpha) are given by (alpha)(,T) = 0.32 (+OR -) 0.11 (0.78 (+OR-) 0.11), applied to the major jet axis, and (alpha)(,N) = -0.25 (+OR-) 0.05 (-0.21 (+OR-) 0.05), applied to the normal to the reconstructed event plane, for (gamma)-direct (continuum) events. These results are in good agreement with QCD.
- Pub Date:
- March 1982
- Physics: Elementary Particles and High Energy