-> Experimentalphysik -> Gruppe Drees/Becks -> Wuppertaler DELPHI Gruppe -> Perturbative QCD

Measurement of the strong coupling alpha_s and its energy dependence from the four jet rate of hadronic events with the DELPHI detector at LEP

U. Flagmeyer, J. Drees, K. Hamacher, O. Passon, R. Reinhardt and D. Wicke

Hadronic events from the data collected with the Delphi detector at Lep within an energy range from 89GeV to 207GeV are selected and their jet rates are determined. The four jet rate is compared to next to leading order calculations. Studies on the influence of the renormalisation scale mu are performed confirming previous Delphi results on optimised scales. Applying scale optimisation methods allows a precise measurement of the strong coupling from Lep1 data. By including Lep2 data the running of alpha_s from four jet events is accessible. The results in O(alpha_s^3) are in good agreement with previous, statistically uncorrelated measurements based on three jet final states.

Full Text with Figures

Postscript DELPHI 2001-059 CONF 487 (~1MB)

Individual Figures

Figure 1a: sprime distribution (189GeV)
Figure 1b: sprime distribution (200GeV)
Figure 2a: D2 distribution (200GeV)
Figure 2b: D2 distribution (207GeV)
Figure 3: Inclusive 4jet rate (207GeV)
Figure 4: QCD jet rates (91GeV)
Figure 5a: QCD jet rates (133GeV)
Figure 5b: QCD jet rates (189GeV)
Figure 6a: QCD jet rates (200GeV)
Figure 6b: QCD jet rates (207GeV)
Figure 7a: 3jet rate Cambridge (91GeV)
Figure 7b: 4jet rate Cambridge (91GeV)
Figure 7c: 4jet rate Cambridge (189GeV)
Figure 8a: Prediction of Durham 4jet rate with Debrecen
Figure 8b: Prediction of Cambridge 4jet rate with Debrecen
Figure 9a: Dependence of Durham 4jet rate from alpha_s variation
Figure 9b: Dependence of Cambridge 4jet rate from alpha_s variation
Figure 9c: Dependence of Durham 4jet rate from x_mu variation
Figure 9d: Dependence of Cambridge 4jet rate from x_mu variation
Figure 10a: Hadronisation correction to Durham 4jet rate
Figure 10b: Hadronisation correction to Durham 4jet rate
Figure 11a: Optimised scales Durham
Figure 11b: Optimised scales Cambridge
Figure 12a: Fits to the Durham 4jet rate
Figure 12b: Fits to the Cambridge 4jet rate
Figure 13: x_mu dependence of alpha_s for different scale settings
Figure 14: Running of alpha_s

flagmeyer@whep.uni-wuppertal.de

Letzte Änderung: 25 Jun 2001