Measurement of the charged particle multiplicity distribution in hadronic Z decays

• Published in: Physics letters. B Vol. 273; no. 1; pp. 181 - 192
• Main Authors: Deschizeaux, B., Gaitan, V., Farilla, A., Nuzzo, S., Raso, G., Ruggieri, F., Hu, H., Lin, J., Wang, T., Lehraus, I., Lusiani, A., Marchioro, A., Meyer, T., Nash, J., Ranjard, F., Rothberg, J., Wasserbaech, S., Witzeling, W., Bardadin-Otwinowska, M., Bencheikh, A.M., El Fellous, R., Falvard, A., Guicheney, C., Jousset, J., Montret, J.-C., Stimpfl, G., Efthymiopoulos, I., Blondel, A., Fouque, G., Rumpf, M., Veitch, E., Parrini, G., Georgiopoulos, C., Sawyer, L., Antonelli, A., Baldini, R., Campana, P., Cerutti, F., Felici, G., Murtas, G.P., Zografou, P., Altoon, B., Halley, A.W., ten Have, I., Raine, C., Turnbull, R.M., Braun, O., Hepp, V., Wunsch, M., Belk, A.T., Beuselinck, R., Hassard, J.F., Girtler, P., Foster, F., Keemer, N.R., Sloan, T., Raab, J., Renk, B., Schmidt, H., Benchouk, C., Bernard, V., Etienne, F., Rousseau, D., Talby, M., Adlung, S., Brown, D., Dehning, B., Jahn, A., Lange, E., Lauber, J., Männer, W., Chen, X., Cordier, A., Grivaz, J.-F., Gros, M.-H., Zomer, F., Amendolia, S.R., Dell'Orso, R., Forti, F., Tenchini, R., Verdini, P.G., Green, M.G., Botterill, D.R., Clifft, R.W., Edwards, M., Fisher, S.M., Jones, T.J., Norton, P.R., Perlas, J.A., Roussarie, A., Combley, F., Hatfield, F., Parker, D., Grupen, C., Ganis, G., Bellantoni, L., Cinabro, D., Gao, Y.S., LeClaire, B.W., Zobernig, G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 12.12.1991; Elsevier
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/0370-2693(91)90575-B

The charged particle multiplicity distribution of hadronic Z decays was measured on the peak of the Z resonance using the ALEPH detector at LEP. Using a model independent unfolding procedure the distribution was found to have a mean 〈 n〉=20.85±0.24 and a dispersion D=6.34±0.12. Comparison with lower energy data supports the KNO scaling hypothesis in the energy range s =29−91.25 GeV. At s =91.25 GeV the shape of the multiplicity distribution is well described by a log-normal distribution, as predicted from a cascading model for multi-particle production. The same model also successfully describes the energy dependence of the mean and width of the multiplicity distribution. A next-to-leading order QCD prediction in the framework of the modified leading-log approximation and local parton-hadron duality is found to fit the energy dependence of the mean but not the width of the charged multiplicity distribution, indicating that the width of the multiplicity distribution is a sensitive probe for higher order QCD or non-perturbative effects.