Multiplicities, fluctuations and QCD: Interplay between soft and hard physics?

✍ Scribed by W. Kittel; S.V. Chekanov; D.J. Mangeol; W.J. Metzger

• Book ID: 104355536
• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 770 KB
• Volume: 71
• Category: Article
• ISSN: 0920-5632
• DOI: 10.1016/s0920-5632(98)00328-4

✦ Synopsis

for the L3 Collaboration Multiplicity fluctuations are studied both globaly (in terms of high-order moments) and locally (in terms of small phase-space intervals). The ratio of cumulant factorial to factorial moments of the charged-particle multiplicity distribution shows a quasi-oscillatory behaviour similar to that predicted by the NNLLA of perturbative QCD. However, an analysis of the sub-jet multiplicity distribution at perturbative scales shows that these oscillations cannot be related to the NNLLA prediction. We investigate how it is possible to reproduce the oscillations within the framework of Monte-Carlo models. Furthermore, local multiplicity fluctuations in angular phasespace intervals are compared with "Monte-Carlo models and with first-order QCD predictions. While JETSET reproduces the experimental data very well, the predictions of the Double Leading Log Approximations and estimates obtained in Modified Leading Log Approximations deviate significantly from the data.