Negative binomials and multiplicity distributions in 250 GeV/cK + and π+ interactions on Al and Au nuclei

The negative binomial distribution (NBD) is fitted to all charged and to negative particle multiplicity distributions in restricted rapidity intervals, both in the forward and backward c.m. hemispheres of positive meson interactions on Al and Au nuclei. For negative particle multiplicity distributions, the NBD parameters are also determined as a function ofn _g, the number of grey tracks, corresponding to varying number of intranuclear collisions. The data are interpreted in terms of the clan picture of Giovannini and Van Hove and compared to the MCMHA and Fritiof models. Both models reproduce quite well the global multiplicity distributions, but not when sub-samples are considered with fixed number of grey tracks. Regularities are better visible on the parton than on the particle level.     

A study of four- and six-body reactions in π+ andK + p interactions at 250 GeV/c

Data on the reactions (K ⁺/π⁺)p→(K ⁺/π⁺)pπ⁺π^- and (K ⁺/π⁺)p→(K ⁺/π⁺)p2π⁺2π^-, obtained with the European Hybrid Spectrometer, are presented and compared with data at lower energies. The contribution of beam and target diffractive dissociation and double Pomeron exchange, and porperties of these reactions are discussed.     

Factorial moments and correlations in meson-nucleus interactions at 250 GeV/c

A sample of 8000 interactions of 250 GeV/c π⁺ andK ⁺ mesons on Al and Au nuclei, is used to search for intermittency effects by calculating the normalized factorial moments of order two to four. No significant effect is observed in the higher moments. Two-body rapidity correlations and Bose-Einstein correlations in these interactions are presented.     

Bose-Einstein correlations inK + p and π+ p at 250 GeV/c

Two-pion correlations are studied for pions of like charge inK ⁺ p andπ ⁺ p collisions at 250 GeV/c. An enhanced production is observed at small momentum difference and is attributed to Bose-Einstein interference between identical particles. A systematic study is presented on the influence of parametrization and reference sample. Interpreted in terms of the Kopylov-Podgoretskii parametrization a size of the emitting regionr _K ≈1.4 fm is found. The Lorentz invariant parametrization of Goldhaber givesr _G ≈0.8 fm. With fixed parametrization, similarity is found for hadronhadron,e ⁺ e ^? and lepton-hadron collisions. No multiplicity or angular dependence is found at our energy.     

Charge and energy flow in π+ p,K + p andpp interactions at 250 GeV/c

We present data on the flow of energy and charge in π⁺ p,K ⁺ p andpp interactions at 250 GeV/c. The energy and charge flow in the beam c.m. hemisphere is analysed in terms of the cluster-invariant Bialas-Ochs-Stodolsky variable λ=cot θ/E _jet. The profile functionsdQ/dλ anddE/dλ indicate a widening inp _T of jets between 32 and 250 GeV/c incident laboratory momentum, whereas the ratiodQ/dE is energy independent. The data are compared to μp deep-inelastic scattering resutls and to expectations from the single string LUND model, the Dual Parton Model and the two-string LUND model (FRITIOF).     

Neutral kaon production inK + p and π+ p interactions at 250 GeV/c

The inclusive production of neutral kaons is studied inK ⁺ p and π⁺ p interactions at 250 GeV/c. Total and semi-inclusive cross sections and average kaon multiplicities are presented and compared with the data at lower energies. The longitudinal and transverse momentum distributions and their energy dependence are analyzed. The results are interpreted in the framework of recent parton models.     

Factorial moments,cumulants and correlation integrals in π+ p andK + p interactions at 250 GeV/c

A selected sample of 59200 π⁺ p andK ⁺ p nonsingle-diffrative interactions at \(\sqrt s \) =22 GeV is used to investigate one, two- and three-dimensional factorial moments, factorial cumulant moments, as well as correlation integrals. The rise of factorial moments and cumulants with decreasing phase-space volume is stronger when evaluated in three than in lower dimensions. Ratios of slopes are easier to obtain than the slopes themselves. Contrary to earlier findings, they turn out to depend on the dimension. The order dependence of the averaged ratios is better described by a Lévy stable law solution with μ=1.6 than by Gaussian approximation of the α-model (μ=2) or a second order phase transition (μ=0), but values μ>2 inconsistent with Lévy-type fluctuations are reached in a three-dimensional analysis. The multiparticle contributions to the factorial moments are calculated by means of factorial cumulant moments. A particular improvement of the method is that of correlation (or density) integrals. It leads to the conclusion that Bose-Einstein interference plays an important role in the intermittency effect, but indication is found for an interpretation alternative to the conventional view of Bose-Einstein correlations.     

Rapidity correlations in π+ p,K + p andpp interactions at 250 GeV/c

Two- and three-particle rapidity correlations are analyzed inK ⁺ p and π⁺ p-interactions at 250 GeV/c. The main contribution to the two- and three-particle correlation functions comes from mixing of events of different multiplicity. The (short range) two-particle correlation remaining after exclusion of mixing is significantly larger for (+?) than for the equal charge combinations, and is positive for a wider range in rapidity difference. FRITIOF and a 2-string DPM are excluded by our data. A quark-gluon (multi-)string model can describe our inclusive correlation function, but needs to be tuned on the short range part. The multiplicity mixing part increases much faster with increasing energy than the short range part. In the central region, our correlation is similar to that observed ine ⁺ e ^? and μp collisions at similar energy.     

Collective sea-gull effect in πp interactions at 250 GeV/c

A collective “sea-gull” effect is observed for a system of fast hadrons produced in the fragmentation regions of nondiffractive π⁺p-interactions at 250 GeV/c. The effect is not reproduced by the FRITIOF fragmentation model in its details. It is demonstrated that hard-like processes, both in the collision phase and in the fragmentation phase, are not properly treated in the model.