2003/07/01 by The DELPHI Collaboration, J. Abdallah · 4 citations
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex
paper · pdf · doi:10.1140/epjc/s2003-01198-0
published as Eur.Phys.J.C29:285-312,2003 · 45 pages, 17 figures, Accepted by Eur. Phys. J. C
openalex publication_date 2003/07/01 · arxiv created 2003/07/17 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
Infrared and collinear safe event shape distributions and their mean values are determined in e+e- collisions at centre-of-mass energies between 45 and 202 GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, alphas is extracted from the mean values and shapes. In an alternative approach, renormalisation group invariance (RGI) is used as an explicit constraint, leading to a consistent description of mean values without the need for sizeable power corrections. The QCD beta-function is precisely measured using this approach. From the DELPHI data on Thrust, including data from low energy experiments, one finds beta0 = 7.86 +/- 0.32 for the one loop coefficient of the beta-function or, assuming QCD, nf = 4.75 +/- 0.44 for the number of active flavours. These values agree well with the QCD expectation of beta0=7.67 and nf=5. A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5 GeV.