Study of gluon fragmentation and colour octet neutralization in DELPHI

Using the full statistics of the DELPHI experiment at $\sqrt{s}=91 GeV$ 3-jet events are selected and gluon respectively quark jet enriched subsamples are defined. The leading systems of the two kinds of jets are determined using rapidity gaps. The sum of charges of the leading systems is studied. It is found that for gluon-jets there is a significant excess of leading systems with total charge zero when compared to Monte Carlo simulations with JETSET. The corresponding leading systems of quark-jets do not exhibit such an excess. The mass spectra of the leading systems with total charge zero are studied.Comment: 8 pages, 6 figures (in eps) talk given at XXXI International Symposium on Multiparticle Dynamics, Sep. 1-7, 2001, Datong China URL http://ismd31.ccnu.edu.cn

How Good are Present Analytical QCD-Predictions on Fluctuations in Angular Intervals ?

Results on two-particle angular correlations in jet cones and on multiplicity fluctuations in one- and two- dimensional angular intervals, delivered by three experiments (DELPHI, L3 and ZEUS, at $\sqrt{s}$ from few to 183 GeV) are compared to present existing analytical QCD calculations, using the LPHD hypothesis. Two different types of functions have been tested. While the differentially normalized correlation functions show substantial deviations from the predictions, a globally normalized correlation function agrees surprisingly well. The role of the QCD parameters $\alpha_s$, $\Lambda$ and $n_f$ is discussed. The necessity to include full energy-momentum conservation into the analytical calculations is stressed.Comment: 13 pages (LaTeX), 11 figures, uses sprocl.sty. Miniraporteur-talk given at the Internat. Symposium of Multiparticle Dynamics, Delphi, Greece, 6-11 Sept. 1998 (to appear in Proceedings

Investigation of Bose-Einstein Correlations in 3 jet events with the DELPHI detector

A preliminary investigation of Bose-Einstein correlations in 3 jet events has been made by analysing the collected data at the $Z^0$ peak from '94 and '95 and the calibration runs during the LEP2 period from '97 to 2000. Three methods were used to extract two-particle correlation functions. No significant difference was found between quark and gluon jets for all three methods.Comment: 6 pages, 2 figures in ps and 1 in eps, talk given at XXXI International Symposium on Multiparticle Dynamics, Sept 1-7, 2001, Datong China. see http://ismd31.ccnu.edu.cn

Multiplicity dependence of correlation functions in \bar{p}p reactions at sqrt(s) = 630 GeV

Discussions about Bose-Einstein correlations between decay products of coproduced W-bosons again raise the question about the behaviour of correlations if several strings are produced. This is studied by the multiplicity dependence of correlation functions of particle pairs with like-sign and opposite-sign charge in \bar{p}p reactions at sqrt{s} = 630 GeV.Comment: 11 pages latex, 4 figs, includes elsart.cls, submitted to Phys Lett

Intermittency in a single event

The possibility to study intermittency in a single event of high multiplicity is investigated in the framework of the $\alpha-$model. It is found that, for cascade long enough, the dispersion of intermittency exponents obtained from individual events is fairly small. This fact opens the possibility to study the distribution of the intermittency parameters characterizing the cascades seen (by observing intermittency) in particle spectra.Comment: 7 pages, latex, 2 figures available on request by e-mai

Intermittency in Branching Processes

We study the intermittency properties of two branching processes, one with a uniform and another with a singular splitting kernel. The asymptotic intermittency indices, as well as the leading corrections to the asymptotic linear regime are explicitly computed in an analytic framework. Both models are found to possess a monofractal spectrum with $\varphi_{q}=q-1$. Relations with previous results are discussed.Comment: 20 pages, UCLA93/TEP/2

Enhanced Event-by-Event Fluctuations in Pion Multiplicity as a Signal of Disoriented Chiral Condensates at RHIC

The factorial moments of the pion multiplicity distributions are calculated with HIJING and UrQMD and found to be independent of the pT range included, in contrast to recent simulations with the linear sigma model which leads to large enhancements for pions with transverse kinetic energies below 200 MeV. This supports the use of the ratio of the factorial moments of low and high pT pions as a signal of ``new'' physics at low momentum scales, such as the formation of disoriented chiral condensates.Comment: 4 pages total, incl 4 eps figures ([email protected]