We present a study of the inclusive production of neutral pions and charged particles from 112 000 hadronic Z 0 decays. The measured inclusive momentum distributions can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results to e + e − data between √ s = 9 and 91 GeV, we findfind that the evolution of the spectra with center of mass energy is consistent with the QCD predictions.
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Error is dominated by systematic uncertainties.
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The production of π±,K±,p has been measured in p+Be and p+Au collisions for comparison with central Si+Au collisions. The inverse slope parameters T0 obtained by an exponential fit to the invariant cross sections in transverse mass are found to be, T0p,K+,ππ∼140–160 MeV in p+A collisions, whereas in central Si+Au collisions, T0p,K+∼200–220 MeV >T0ππ∼140–160 MeV at midrapidity. The π± and K+ distributions are shifted backwards in p+Au compared with p+Be. A gradual increase of (dn/dy)K+ per projectile nucleon is observed from p+Be to p+Au to central Si+Au collisions, while pions show no significant increase.
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The multiplicity distributions of charged particles in restricted rapidity intervals inZ0 hadronic decays measured by the DELPHI detector are presented. The data reveal a shoulder structure, best visible for intervals of intermediate size, i.e. for rapidity limits around ±1.5. The whole set of distributions including the shoulder structure is reproduced by the Lund Parton Shower model. The structure is found to be due to important contributions from 3-and 4-jet events with a hard gluon jet. A different model, based on the concept of independently produced groups of particles, “clans”, fluctuating both in number per event and particle content per clan, has also been used to analyse the present data. The results show that for each interval of rapidity the average number of clans per event is approximately the same as at lower energies.
Data for both hemispheres.
Data for both hemispheres.
Data for both hemispheres.
This paper presents and contrasts features of the inelastic nuclear reactions of 200 GeV/nucleon 16 O and 32 S ions with emulsion nuclei. Both the multiplicities of shower particles and the extent of target fragmentation have been studied for varying degress of disruption of the projectile nuclei. The results may be interpreted within a simple geometrical model. In particular the rapidity distributions of those events which exhibit complete projectile break-up without any overt sign of low-energy target fragmentation have been determined. The interaction of secondary projectile fragments of charge two or more issuing from oxygen interactions were also studied and the mean free paths in emulsion of the primary 16 O and 32 S ions and all such fragments have been compared to those predicted by a simple Glauber model.
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Data on the multiplicity and inclusive spectra of γ produced in inelastic pNe20 and pN interactions at 300 GeV are presented. The γ multiplicity for pNe20 interactions is 11.43±0.23, and the ratio of 〈nγ〉 for pNe20 and pN interactions is 1.48±0.05. From an analysis of the effective-mass distributions, 〈nπ0〉=4.91±0.52 and 〈nη0〉=1.47±0.33. In fact, η0 production is much higher in pNe20 interactions [R(η0π0)=0.66±0.12 for np≥21] than in pN interactions [R(η0π0)=0.06±0.04]. No η′(958) signal is seen. Strong correlations between 〈nγ〉 and np, the number of secondary protons, are observed, primarily from the central and target fragmentation regions. Inclusive y* and p⊥ spectra are analyzed and evidence for low-energy cascading and rescattering of fast particles in the projectile fragmentation region is discussed. The data are compared to the predictions of the additive quark model, the Lund model, and the dual parton model.
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GAMMA-MULTIPLICITY FOR (PROTON-NUCLEON)-INTERACTION WAS OBTAINED AT AVERAGING OVER (PP) AND (PN) EVENTS, AND THEN WAS USED IN THE PRESENTED RATIO.
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Data on multiplicity, correlations, and inclusive spectra of KS0 mesons and Λ0(Λ¯0) hyperons produced with xF≤0 in inelastic pNe20 and pN interactions at 300 GeV are presented and compared. The inclusive cross sections for pNe20 (pN) with xF≤0 are 61.1±2.8 mb (3.34±0.64 mb) for KS0, 40.8±2.5 mb (1.89±0.29 mb) for Λ0, and 3.9±0.5 mb (0.31±0.08 mb) for Λ¯0. The multiplicity ratio for pNe20 and pN interactions is 1.58±0.16 for KS0, 1.95±0.23 for Λ0, and 1.12±0.43 for Λ¯0. We have observed the Σ0(1193) hyperon and measured the average multiplicity (nΣ0=0.049±0.027) for xF≤0. We have also observed the strange resonances K*(892), K*(1415), and Σ*(1385) with xF≤0 and measured the fraction of V0 coming from each resonance. Λ0 polarization for xF≤0 is measured and shows a decrease as p⊥ increases [pΛ(pNe20)≈−0.25 at p⊥=1.5 GeV/c], in agreement with other experiments which measure polarization in the region xF≫0. Since (43±7)% of the Λ0 are produced in Σ0→Λ0γ decays, the Λ0 polarization is significantly greater than the measured values. Experimental results are compared to predictions of the Lund model and the dual parton model of soft hadron-nucleus and hadron-nucleon interactions.
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Axis error includes +- 0.0/0.0 contribution (NOT GIVEN).
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Hadronic decays of Z 0 bosons are studied in the Delphi detector. Global event variables and singel particles inclusive distributions are compared with QCD-based predictions. The mean charged multiplicity is found to be 20.6±1.0 (stat+syst). The mean values of the sphericity, aplanarity, thrust, minor value, p in T and p out T are compared with values found at lower energy e + e − colliders.
Corrected Sphericity distribution. Statistical errors only.
Corrected Aplanarity distribution. Statistical errors only.
Corrected Q3-Q2 distribution. Statistical errors only.
We report on properties of hadronic events from e + e − annihilation observed by the ALEPH detector at the large Electron Positron Collider at CERN. The center-of-mass energy was s =91.0−91.3 GeV . Measured distributions of the global event-shape variables sphericity, aplanarity, thrust and minor value, and of the inclusive variables x p , p ⊥ in , p ⊥ out and y are presented. We measure a mean charged multiplicity in hadronic events of 〈 N ch 〉=21.3±0.1 (statistical)±0.6 (systematic). The data are in good agreement with QCD-based models which use the leading-logarithm approximation, and are less well described by a model using O( α s 2 ) QCD.
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Multiplicity distributions of charged particles produced in the pseudorapidity range 0.9 < η lab < 5.5 were measured in oxygen-nucleus collisions for Al, Ag, and W target nuclei at incident energies of 60 and 200 GeV per nucleon. The multiplicity differential cross sections and the pseudorapidity distributions as a function of transverse energy are presented for the various target nuclei. The correlation between charged multiplicity and transverse energy is studied as a function of transverse energy. Data are compared with predictions of the IRIS and FRITIOF generators.
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The production of the meson resonances ϱ(770) (all three charge states), η(550), ω(783) andf2(1270) in\(\bar v\) Ne and ν Ne charged current interactions is investigated in a bubble chamber experiment with BEBC at CERN. Except for thef2, the main features of resonance production are reasonably well described by the Lund model, although the average resonance multiplicities are overestimated by the model by (67±30)%. The average multiplicities of all resonances, including thef2, are well reproduced by a semiempirical model, whose parameters were determined from hadron interaction data.
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