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, y(1). 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 y(0) (< y(1)) so that subjets are resolved. The properties of the jets (subjet multiplicities [N-q], [N-g] and rates R(n)(g)((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 y(0) is sufficiently large to keep non-perturbative effects small. In particular, the ratio [N-g - 1]/[N-q - 1], which to leading order in QCD is given by the ratio of colour factors C-A/C-F = 9/4, is measured to be 1.96 +/- 0.15 for y(0) = 2 . 10(-3), but falls to 1.29 +/- 0.03 for y(0) = 1.6 . 10(-5).

D., B., D., C., I., D., D., D., P., G., C., G., et al. (1995). Study of the Subjet Structure of Quark and Gluon Jets. PHYSICS LETTERS. SECTION B, 346(3-4), 389-398 [10.1016/0370-2693(95)00037-L].

Study of the Subjet Structure of Quark and Gluon Jets

BOTTIGLI, UBALDO;CIOCCI, MARIA AGNESE;MARROCCHESI, PIER SIMONE;
1995-01-01

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, y(1). 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 y(0) (< y(1)) so that subjets are resolved. The properties of the jets (subjet multiplicities [N-q], [N-g] and rates R(n)(g)((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 y(0) is sufficiently large to keep non-perturbative effects small. In particular, the ratio [N-g - 1]/[N-q - 1], which to leading order in QCD is given by the ratio of colour factors C-A/C-F = 9/4, is measured to be 1.96 +/- 0.15 for y(0) = 2 . 10(-3), but falls to 1.29 +/- 0.03 for y(0) = 1.6 . 10(-5).
1995
D., B., D., C., I., D., D., D., P., G., C., G., et al. (1995). Study of the Subjet Structure of Quark and Gluon Jets. PHYSICS LETTERS. SECTION B, 346(3-4), 389-398 [10.1016/0370-2693(95)00037-L].
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11365/37865
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo