Study of the subjet structure of quark and gluon jets

D. Buskulic, D. Casper, I. De Bonis, D. Decamp, P. Ghez, C. Goy, J. P. Lees, M. N. Minard, P. Odier, B. Pietrzyk, F. Ariztizabal, M. Chmeissani, J. M. Crespo, I. Efthymiopoulos, E. Fernandez, M. Fernandez-Bosman, V. Gaitan, Ll Garrido, M. Martinez, S. OrteuA. Pacheco, C. Padilla, F. Palla, A. Pascual, J. A. Perlas, F. Sanchez, F. Teubert, D. Creanza, M. de Palma, A. Farilla, G. Iaselli, G. Maggi, N. Marinelli, S. Natali, S. Nuzzo, A. Ranieri, G. Raso, F. Romano, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, G. Zito, X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao, G. Bonvicini, M. Cattaneo, P. Comas, P. Coyle, H. Drevermann, A. Engelhardt, R. W. Forty, M. Frank, G. Ganis, M. Girone, R. Hagelberg, J. Harvey, R. Jacobsen, B. Jost, J. Knobloch, I. Lehraus, M. Maggi, C. Markou, E. B. Martin, P. Mato, H. Meinhard, A. Minten, R. Miquel, P. Palazzi, J. R. Pater, P. Perrodo, J. F. Pusztaszeri, F. Ranjard, L. Rolandi, D. Schlatter, M. Schmelling, W. Tejessy, I. R. Tomalin, R. Veenhof, A. Venturi, H. Wachsmuth, W. Wiedenmann, T. Wildish, W. Witzeling, J. Wotschack, Z. Ajaltouni, M. Bardadin-Otwinowska, A. Barres, C. Boyer, A. Falvard, P. Gay, C. Guicheney

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45 Citations (Scopus)

Abstract

Measurements of the subjet structure of quark and gluon jets in hadronic Z decays are presented. The analysis is based on one million hadronic events recorded by the Aleph detector. Roughly symmetric three-jet events are selected with a coarse jet-resolution cut-off, y1. Gluon jets are identified with a purity of 94.6% in those events where evidence of long-lived heavy-flavour hadrons in the other two jets is found. The jets are then analyzed using a smaller cut-off y0 (< y1) so that subjets are resolved. The properties of the jets (subjet multiplicities (Nq), (Ng) and rates Rng(q) for n = 1, 2, 3, 4) are determined and are found to be in good agreement with the expectations of perturbative QCD as long as the subjet resolution parameter y0 is sufficiently large to keep non-perturbative effects small. In particular, the ratio (Ng - 1) (Nq - 1), which to leading order in QCD is given by the ratio of colour factors CA CF = 9 4, is measured to be 1.96 ± 0.15 for y0 = 2 · 10-3, but falls to 1.29 ± 0.03 for y0 = 1.6 · 10-5. © 1995.
Original languageEnglish
Pages (from-to)389-398
JournalPhysics Letters B
Volume346
Issue number3-4
DOIs
Publication statusPublished - 9 Mar 1995

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