Direct Tests of Quantum Chromodynamics in High - Electron-Positron Annihilation at PETRA.
With the TASSO detector at PETRA, we have studied QCD effects in the hadronic channel of e('+)e('-) annihilation. In addition to events with 2 jets of hadrons, we have observed 3-jet events which are naturally described in the context of QCD as manifestations of the process e('+)e('-) (-- ->) qqg. By studying distributions sensitive to the rate of 3-jet production in the range of 27 GeV < W < 37 GeV, we determined the strong coupling constant, (alpha)(,s) to be. (alpha)(,s) = 0.17 (+OR-) 0.01 (+OR-) 0.03. where 0.01 is the statistical error, and 0.03 is the systematic error. Comparing predictions of QCD models with the data, we found that the models accurately described the observed energy dependence of numerous distributions, as well as detailed properties of 3-jet events. By studying angular distributions of jet axes in 3-jet events, we found that our data were consistent with spin-1 gluons (0.9(sigma)) while being in strong disagreement with the hypothesis of spin-0 gluons (4.5(sigma)).
- Pub Date:
- Physics: Elementary Particles and High Energy