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Measurements have been made of inclusive 525 GeV π− interactions in emulsion. The results are compared to proton-emulsion and lower energy pion-emulsion data. Average multiplicities of relativistic shower particles increase with increasing energy, although with a somewhat steeper slope above 60 GeV than at lower energies. The ratio 〈ns〉p/〈ns〉π∼1.1 over the energy range 60–525 GeV. The ratio of the dispersion in the multiplicity distribution to the average multiplicity is the same for proton and pion collisions in emulsion, and is independent of projectile energy. The shape of the shower particle multiplicity distribution does not vary significantly with energy, and KNO scaling appears to hold over the energy range 60–525 GeV. The shower particle pseudorapidity distributions are independent of the beam energy in the target and projectile fragmentation regions, and both the pseudorapidity and multiplicity distributions agree reasonably well with the fritiof model predictions for 525 GeV pions. The dependence of the shower particle multiplicity 〈ns〉 on the number of heavy tracks Nh appraoches saturation as the total shower particle energy becomes a significant fraction of √s , and the pseudorapidity distributions shift toward smaller 〈η〉 with increasing numbers of grey and black tracks at 525 GeV. Neither the average number 〈Nh〉 nor the multiplicity distributions of the heavily ionizing tracks vary significantly with energy, and the normalized angular distributions of grey and black tracks are independent of the type of projectile or projectile energy.
NUCLEUS means average nuclei of BR-2 emulsion.
NUCLEUS means average nuclei of BR-2 emulsion.
NUCLEUS means average nuclei of BR-2 emulsion.
The energy and centrality dependence of local particle pseudorapidity densities as well as validity of various parametrizations of the distributions are examined. The dispersion, σ, of the rapidity density distribution of produced particles varies slowly with centrality and is 0.80, 0.98, 1.21 and 1.41 for central interactions at 3.7, 14.6, 60 and 200A GeV incident energy, respectively, σ is found to be independent of the size of the interacting system at fixed energy. A novel way of representing the window dependence of the multiplicity as normalized variance versus inverse average multiplicity is outlined.
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NUCLEUS IS AGBR, CENTRAL EVENTS.
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We present an analysis of multiplicity distributions of charged particles produced inZ0 hadronic decays. The results are based on the analysis of 82941 events collected within 100 MeV of theZ0 peak energy with the OPAL detector at LEP. The charged particle multiplicity distribution, corrected for initial-state radiation and for detector acceptance and resolution, was found to have a mean 〈nch〉=21.40±0.02(stat.)±0.43(syst.) and a dispersionD=6.49±0.02(stat.)±0.20(syst.). The shape is well described by the Lognormal and Gamma distributions. A negative binomial parameterisation was found to describe the shape of the multiplicity distribution less well. A comparison with results obtained at lower energies confirms the validity of KNO(-G) scaling up to LEP energies. A separate analysis of events with low sphericity, typically associated with two-jet final states, shows the presence of features expected for models based on a stochastic production mechanism for particles. In all cases, the features observed in the data are well described by the Lund parton shower model JETSET.
Distribution for whole event. The data at multiplicites 2 and 4 come from Monte Carlo data.
Distribution for single hemisphere.
Distribution for whole event. The data at multiplicites 2 and 4 come from Monte Carlo data.. Contributions from K0S and LAMBDA decays have been subtracted.
A factorial moment analysis has been performed on the differential multiplicity distributions of hadronic final states of the Z 0 recorded with the OPAL detector at LEP. The moments of the one-dimensional rapidity and the two-dimensional rapidity versus azimuthal angle distributions are found to exhibit “intermittent” behaviour attributable to the jet structure of the events. The moments are reproduced by both parton shower and matrix element QCD based hadronisation models. No evidence for fluctuations beyond those attributable to jet structure is observed.
Corrected factorial moments of the rapidity distribution with respect to the sphericity axis. The errors shown are statistical only but include the statistical error onthe correction factor, added in quadrature.
Corrected factorial moments of the rapidity distribution with respect to the electron beam axis. The errors shown are statistical only but include the statistical error onthe correction factor, added in quadrature.
Corrected factorial moments of the rapidity (with respect to the sphericityaxis) versus PHI distribution. For each point the NUMBER of bins are constructe d from equal numbers of YRAP and PHI bins. The errors shown are statistical only but include the statistical error onthe correction factor, added in quadrature.
Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.
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NUCLEUS IS C6J.
NUCLEUS IS C6J.
NUCLEUS IS C6J.
Topological cross sections and characteristics of charged particle multiplicity distributions for¯nn andnn interactions and¯nn annihilations at 6·1 GeV/c are presented. KNO-distributions for¯nn andnn interactions are very similar. Characteristics for¯nn and¯pp annihilations are identical at equal energies.
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