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Abdallah, J.; Abreu, P.; Adam, W.; Adzic, P.; Albrecht, T.; Alderweireld, T.; Alemany-Fernandez, R.; Allmendinger, T.; Allport, P.P.; Almehed, S.; Amaldi, U.; Amapane, N.; Amato, S.; Anashkin, E.; Andreazza, A.; Andringa, S.; Anjos, N.; Antilogus, P.; Apel, W.D.; Arnoud, Y.; Ask, S.; Asman, B.; Augustin, J.-E.; Augustinus, A.; Baillon, P.; Ballestrero, A.; Bambade, P.; Barbier, R.; Bardin, D.; Barker, G.; Baroncelli, A.; Battaglia, M.; Baubillier, M.; Becks, K.H.; Begalli, M.; Behrmann, A.; Bellunato, T.; Benekos, N.; Benvenuti, A.; Berat, C.; Berggren, M.; Berntzon, L.; Bertrand, D.; Besancon, M.; Besson, N.; Bloch, D.; Blom, M.; Bonesini, M.; Boonekamp, M.; Booth, P.S.L.; Borisov, G.; Botner, O.; Bouquet, B.; Bowcock, T.J.V.; Boyko, I.; Bracko, M.; Brenner, R.; Brodet, E.; Brodzicka, J.; Bruckman, P.; Brunet, J.M.; Bugge, L.; Buschmann, P.; Calvi, M.; Camporesi, T.; Canale, V.; Carena, F.; Carimalo, C.; Castro, N.; Cavallo, F.; Chapkin, M.; Charpentier, P.; Checchia, P.; Chierici, R.; Chliapnikov, P.; Chung, S.U.; Cieslik, K.; Collins, P.; Contri, R.; Cosme, G.; Cossutti, F.; Costa, M.J.; Crawley, B.; Crennell, D.; Cuevas, J.; d'Hondt, J.; Dalmau, J.; da Silva, T.; da Silva, W.; Della Ricca, G.; de Angelis, A.; de Boer, W.; de Clercq, C.; de Lotto, B.; de Maria, N.; de Min, A.; de Paula, L.; Di Ciaccio, L.; Di Simone, A.; Doroba, K.
The European physical journal. C, Particles and fields, 07/2003, Letnik: 29, Številka: 3Journal Article
Infrared and collinear safe event shape distributions and their mean values are determined in \({\mathrm{e^+e^-}}\) collisions at centre-of-mass energies between 45 and 202GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, \(\alpha_s\) 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 \\beta_0 = 7.86 \pm 0.32\ for the one loop coefficient of the \(\beta\)-function or, assuming QCD, \n_{\mathrm{f}} = 4.75 \pm 0.44 \ for the number of active flavours. These values agree well with the QCD expectation of \(\beta_0=7.67\) and \(n_{\mathrm{f}}=5\). A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5GeV.
