466 research outputs found
Study of gluon fragmentation and colour octet neutralization in DELPHI
Using the full statistics of the DELPHI experiment at 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
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 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
Intermittency in a single event
The possibility to study intermittency in a single event of high multiplicity
is investigated in the framework of the 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
Internal cumulants for femtoscopy with fixed charged multiplicity
A detailed understanding of all effects and influences on higher-order
correlations is essential. At low charged multiplicity, the effect of a
nonpoissonian multiplicity distribution can significantly distort correlations.
Evidently, the reference samples with respect to which correlations are
measured should yield a null result in the absence of correlations. We show how
the careful specification of desired properties necessarily leads to an
average-of-multinomials reference sample. The resulting internal cumulants and
their averaging over several multiplicities fulfil all requirements of
correctly taking into account nonpoissonian multiplicity distributions as well
as yielding a null result for uncorrelated fixed-N samples. Various correction
factors are shown to be approximations at best. Careful rederivation of
statistical variances and covariances within the frequentist approach yields
errors for cumulants that differ from those used so far. We finally briefly
discuss the implementation of the analysis through a multiple event buffer
algorithm.Comment: 33 pages, 3 figures, 79 reference
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
Transverse-longitudinal HBT correlations in proton-antiproton collisions at root(s) = 630 GeV
Correlations of like-sign pion pairs emerging from proton-antiproton
collisions are analysed in the two-dimensional (q_L,q_T) decomposition of the
three-momentum difference q. While the data cannot be adequately represented by
gaussian, exponential, power-law or Edgeworth parametrisations, more elaborate
ones such as Levy and an exponential with a cross term do better. A two-scale
model using a hard cut to separate small and large scales may indicate a core
that is more prolate than the halo. Consideration not only of the interference
peak at small (q_L,q_T), but also of the shape of the correlation distribution
at intermediate momentum differences is crucial to understanding the data.Comment: 12 pages, 5 figures, uses elsart.cl
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