The charged particle multiplicity in hadronic three-jet events from Z decays is investigated. The topology dependence of the event multiplicity is found to be well described by a modified leading logarithmic prediction. A parameter fit of the prediction to the data yields a measurement of the colour factor ratio C_A/C_F with the result C_A/C_F = 2.261 +/- 0.014 (stat.) +/- 0.036 (exp.) +/- 0.066 (theo.) in agreement with the SU(3) expectation of QCD. The quark-related contribution to the event multiplicity is subtracted from the three-jet event multiplicity resulting in a measurement of the multiplicity of two-gluon colour-singlet states over a wide energy range. The ratios r=N_{gg}(s)/N_{q qbar}(s) of the gluon and quark multiplicities and r^{(1)}=N_{gg}'(s)/N_{q qbar}'(s) of their derivatives are compared with perturbative calculations. While a good agreement between calculations and data is observed for r^{(1)}, larger deviations are found for r indicating that non-perturbative effects are more important for r than for r^{(1)}.
Charged particle multiplicity in three-jet events and two-gluon systems / J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, T. Alderweireld, R. Alemany Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, S. Amato, E. Anashkin, A. Andreazza, S. Andringa, N. Anjos, P. Antilogus, W.D. Apel, Y. Arnoud, S. Ask, B. Asman, J.E. Augustin, A. Augustinus, P. Baillon, A. Ballestrero, P. Bambade, R. Barbier, D. Bardin, G.J. Barker, A. Baroncelli, M. Battaglia, M. Baubillier, K.H. Becks, M. Begalli, A. Behrmann, E. Ben Haim, N. Benekos, A. Benvenuti, C. Berat, M. Berggren, L. Berntzon, D. Bertrand, M. Besancon, N. Besson, D. Bloch, M. Blom, M. Bluj, M. Bonesini, M. Boonekamp, P.S.L. Booth, G. Borisov, O. Botner, B. Bouquet, T.J.V. Bowcock, I. Boyko, M. Bracko, R. Brenner, E. Brodet, P. Bruckman, J.M. Brunet, P. Buschmann, M. Calvi, T. Camporesi, V. Canale, F. Carena, N. Castro, F. Cavallo, M. Chapkin, P.H. Charpentier, P. Checchia, R. Chierici, P. Chliapnikov, J. Chudoba, S.U. Chung, K. Cieslik, P. Collins, R. Contri, G. Cosme, F. Cossutti, M.J. Costa, D. Crennell, J. Cuevas, J. D'Hondt, J. Dalmau, T. da Silva, W. Da Silva, G. Della Ricca, A. De Angelis, W. De Boer, C. De Clercq, B. De Lotto, N. De Maria, A. De Min, L. de Paula, L. Di Ciaccio, A. Di Simone, K. Doroba, J. Drees, G. Eigen, T. Ekelof, M. Ellert, M. Elsing, M.C. Espirito Santo, G. Fanourakis, D. Fassouliotis, M. Feindt, J. Fernandez, A. Ferrer, F. Ferro, U. Flagmeyer, H. Foeth, E. Fokitis, F. Fulda Quenzer, J. Fuster, M. Gandelman, C. Garcia, P.H. Gavillet, E. Gazis, R. Gokieli, B. Golob, G. Gomez Ceballos, P. Goncalves, E. Graziani, G. Grosdidier, K. Grzelak, J. Guy, C. Haag, A. Hallgren, K. Hamacher, K. Hamilton, S. Haug, F. Hauler, V. Hedberg, M. Hennecke, H. Herr, J. Hoffman, S.O. Holmgren, P.J. Holt, M.A. Houlden, K. Hultqvist, J.N. Jackson, G. Jarlskog, P. Jarry, D. Jeans, E.K. Johansson, P.D. Johansson, P. Jonsson, C. Joram, L. Jungermann, F. Kapusta, S. Katsanevas, E. Katsoufis, G. Kernel, B.P. Kersevan, U. Kerzel, B.T. King, N.J. Kjaer, P. Kluit, P. Kokkinias, C. Kourkoumelis, O. Kouznetsov, Z. Krumstein, M. Kucharczyk, J. Lamsa, G. Leder, F. Ledroit, L. Leinonen, R. Leitner, J. Lemonne, V. Lepeltier, T. Lesiak, W. Liebig, D. Liko, A. Lipniacka, J.H. Lopes, J.M. Lopez, D. Loukas, P. Lutz, L. Lyons, J. Macnaughton, A. Malek, S. Maltezos, F. Mandl, J. Marco, R. Marco, B. Marechal, M. Margoni, J.C. Marin, C. Mariotti, A. Markou, C. Martinez Rivero, J. Masik, N. Mastroyiannopoulos, F. Matorras, C. Matteuzzi, F. Mazzucato, M. Mazzucato, R. Mc Nulty, C. Meroni, E. Migliore, W. Mitaroff, U. Mjoernmark, T. Moa, M. Moch, K. Moenig, R. Monge, J. Montenegro, D. Moraes, S. Moreno, P. Morettini, U. Mueller, K. Muenich, M. Mulders, L. Mundim, W. Murray, B. Muryn, G. Myatt, T. Myklebust, M. Nassiakou, F. Navarria, K. Nawrocki, R. Nicolaidou, M. Nikolenko, A. Oblakowska Mucha, V. Obraztsov, A. Olshevski, A. Onofre, R. Orava, K. Osterberg, A. Ouraou, A. Oyanguren, M. Paganoni, S. Paiano, J.P. Palacios, H. Palka, T.H.D. Papadopoulou, L. Pape, C. Parkes, F. Parodi, U. Parzefall, A. Passeri, O. Passon, L. Peralta, V. Perepelitsa, A. Perrotta, A. Petrolini, J. Piedra, L. Pieri, F. Pierre, M. Pimenta, E. Piotto, T. Podobnik, V. Poireau, M.E. Pol, G. Polok, V. Pozdniakov, N. Pukhaeva, A. Pullia, J. Rames, A. Read, P. Rebecchi, J. Rehn, D. Reid, R. Reinhardt, P. Renton, F. Richard, J. Ridky, M. Rivero, D. Rodriguez, A. Romero, P. Ronchese, P. Roudeau, T. Rovelli, V. Ruhlmann Kleider, D. Ryabtchikov, A. Sadovsky, L. Salmi, J. Salt, C. Sander, A. Savoy Navarro, U. Schwickerath, A. Segar, R. Sekulin, M. Siebel, A. Sisakian, G. Smadja, O. Smirnova, A. Sokolov, A. Sopczak, R. Sosnowski, T. Spassov, M. Stanitzki, A. Stocchi, J. Strauss, B. Stugu, M. Szczekowski, M. Szeptycka, T. Szumlak, T. Tabarelli, A.C. Taffard, F. Tegenfeldt, J. Timmermans, L. Tkatchev, M. Tobin, S. Todorovova, B. Tome, A. Tonazzo, P. Tortosa, P. Travnicek, D. Treille, G. Tristram, M. Trochimczuk, C. Troncon, M.L. Turluer, I.A. Tyapkin, P. Tyapkin, S. Tzamarias, V. Uvarov, G. Valenti, P. Van Dam, J. Van Eldik, N. van Remortel, I. Van Vulpen, G. Vegni, F. Veloso, W. Venus, P. Verdier, V. Verzi, D. Vilanova, L. Vitale, V. Vrba, H. Wahlen, A.J. Washbrook, C. Weiser, D. Wicke, J. Wickens, I.G. Wilkinson, M. Winter, M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - 44:3(2005), pp. 311-331. [10.1140/epjc/s2005-02390-x]
Charged particle multiplicity in three-jet events and two-gluon systems
A. Andreazza;C. Meroni;G. Vegni;
2005
Abstract
The charged particle multiplicity in hadronic three-jet events from Z decays is investigated. The topology dependence of the event multiplicity is found to be well described by a modified leading logarithmic prediction. A parameter fit of the prediction to the data yields a measurement of the colour factor ratio C_A/C_F with the result C_A/C_F = 2.261 +/- 0.014 (stat.) +/- 0.036 (exp.) +/- 0.066 (theo.) in agreement with the SU(3) expectation of QCD. The quark-related contribution to the event multiplicity is subtracted from the three-jet event multiplicity resulting in a measurement of the multiplicity of two-gluon colour-singlet states over a wide energy range. The ratios r=N_{gg}(s)/N_{q qbar}(s) of the gluon and quark multiplicities and r^{(1)}=N_{gg}'(s)/N_{q qbar}'(s) of their derivatives are compared with perturbative calculations. While a good agreement between calculations and data is observed for r^{(1)}, larger deviations are found for r indicating that non-perturbative effects are more important for r than for r^{(1)}.
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