E. N. Kladnitskaya

Interaction cross sections and negative pion multiplicities in nucleus-nucleus collisions at 4.2 GeV/c per nucleon

Scanning results ofp, d, he, and12C interactions on Ta plates and in propane are presented. Inelastic cross sections are determined. They agree with geometrical models. General characteristics of pion multiplicity distributions are analyzed and compared with results from nucleon-nucleon interactions. Average multiplicities of negative pions are found to depend on the number of interacting beam nucleons.

Multiplicity, momentum and angular characteristics of π− mesons forpC,dC, αC and CC interactions at 4.2 GeV/c per nucleon

Light ion collisions with carbon target at 4.2 GeV/c/N are studied. Pion multiplicity distributions, momentum and angular spectra are analysed. These data are described in terms of models assuming independent interactions of nucleons from the projectile nucleus with the target.

Features of CC interactions at a momentum of 4.2 GeV/c per nucleon for various degrees of nuclear-collision centrality

The multiplicity, rapidity, and transverse-momentum distributions of secondaries (negative pions and protons) from CC interactions characterized by various numbers of participant protons are presented. It is shown that, in contrast to the mean transverse momenta of protons, the mean transverse momenta of pions depend only slightly on the degree of collision centrality. The shape of the rapidity distributions of negative pions is also weakly dependent on the degree of collision centrality. With decreasing impact parameter, the product protons are found to concentrate in the central rapidity region. The data in question are analyzed within the modified version of the FRITIOF model. It is shown that, as soon as elastic nucleon rescatterings are taken into account, the model describes satisfactorily the experimental features of negative pions and fast protons. The spectra of slow protons are described only qualitatively because of limitations of the evaporation model used here to treat the deexcitation of residual nuclei.

Features of pC interactions at a momentum of 4.2 GeV/c versus the degree of centrality of collisions between protons and carbon nuclei: Multiplicity of secondary particles

New experimental data obtained for the multiplicities of charged pions and protons from the interaction of 4.2-GeV/c protons with a carbon nucleus by using the 2-m propane bubble chamber installed at the High Energy Laboratory (Joint Institute for Nuclear Research, Dubna) are presented versus the degree of collision centrality. The parameter Q defined for each individual event as the difference of the total multiplicities of positively and negatively charged particles without allowing for the multiplicity of evaporated protons whose momentum is less than 0.3 GeV/c is taken for a criterion of the degree of collision centrality. It is shown that, with increasing Q, the multiplicity of positively charged pions and the multiplicity of participant protons from the target nucleus grow considerably; concurrently, the multiplicity of negatively charged pions remains at nearly the same level, while the mean multiplicity of evaporated protons decreases sharply. Our experimental data are compared with the results of calculations based on the cascade-evaporation model and the modified FRITIOF model. Within the FRITIOF model, nonnucleon degrees of freedom in nuclei (Δ+, Δ0 isobars) are taken into account for the first time, and the resulting description of the features of secondary particles appears to be by and large satisfactory.

Analyzing the features of π− mesons and protons from AC interactions at a momentum of p=4.2 GeV/c per projectile nucleon on the basis of the FRITIOF model

The mean multiplicities of π− mesons and protons originating from pC, dC, αC, and CC interactions at a momentum of p=4.2 GeV/c per projectile nucleon and the distributions of these particles in kinematical variables are presented. These experimental distributions are compared with the corresponding predictions obtained on the basis of the FRITIOF model. It is shown that the FRITIOF version used in the present analysis describes satisfactorily our experimental data.

Peripheral and central nucleus-nucleus collisions at 4.2 GeV/c per nucleon

Experimental data on interactions of relativistic p, d, He and C nuclei with carbon and tantalum nuclei are presented. The data come from the 2−m propane bubble chamber with an internal tantalum target. It is found that interaction cross sections for carbon projectile fragments with chargesZ=5,6 are 10% greater than expected. In central C+C collisions and in multinucleon interactions of d, He and C with tantalum a contribution is observed from cumulative interactions irreducible to the superposition of NN-collisions taking into account final state interactions, rescattering effects, etc.

Anisotropic collective flow of Λ-hyperons produced in C+C collisions at 4.2 AGeV/c

Abstract Features of anisotropic collective flow and spectral temperatures have been determined for Λ hyperons emitted from C + C collisions, at incident momentum of 4.2 A GeV / c , measured using the Propane Bubble Chamber of JINR at Dubna. Moreover, characteristics of protons and of negative pions, emitted from those collisions, have been determined and provided for comparison. The directed and elliptic flows of Λ s both agree in sign with the corresponding flows of protons. Parameters of the directed and elliptic flows for Λ s agree further, within errors, with the corresponding parameters for the co-produced protons. This contrasts an earlier finding by the E895 Collaboration of the directed flow being significantly weaker for Λ s than protons, in the much heavier Au + Au system, at comparable incident momentum. Particle spectral temperatures in the C + C collisions have been determined focusing independently on either center-of-mass energy, transverse energy or transverse momentum distributions. For either protons or negative pions, the temperatures were found to be approximately the same, no matter whether the emission of those particles was associated with Λ production or not. Results of the measurements have been compared to the results of simulations within the Quark–Gluon String Model.

Characteristics ofπ− production in the collisions of 4.2 GeV/c/nucleond, α and12C beams with tantalum

One particle distributions ofπ− produced in the collisions of deuterons, alphas, and carbon nuclei with Ta target at 4.2 GeV/c per nucleon momentum, registered in the propane bubble chamber, are presented. Comparison of the data with multiple scattering model and additive quark model is attempted.

Collective flow of protons and negative pions in nucleus–nucleus collisions at momentum of 4.2–4.5A GeV/c

Collective flow of protons and negative pions has been studied within the momentum region of

Features of pC interactions at a momentum of 4.2 GeV/c versus the degree of centrality of a collision between a proton and a carbon nucleus: Kinematical features of secondaries

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