Search

To describe [Formula: see text] interactions with production of three [Formula: see text]-particles at incident neutron kinetic energy of 14 MeV in a nuclear (photo) emulsion, a Monte Carlo model is proposed for four channels of decay of an excited carbon-12 nucleus into three [Formula: see text]-particles. The Monte Carlo calculation results describe well the experimental data on the distribution of the angle between the three-dimensional momenta of all pairs of [Formula: see text]-particles in a collision event, on the distribution of the angle between the projections of the momentum vectors of all pairs of [Formula: see text]-particles in collision event on each of the coordinate planes, on the distribution of the sum of the kinetic energies of all pairs of [Formula: see text]-particles in a collision event, and the distribution of projections of the momenta of [Formula: see text]-particles on the coordinate planes. The best agreement of the Monte Carlo model results with the experimental data is achieved if the direct decay [Formula: see text] and decay through the formation of an intermediate beryllium nucleus [Formula: see text] are generated with equal probabilities, while the excitation energies of 3.04 MeV, 1.04 MeV, and 0.1 MeV for the beryllium nucleus are generated with relative weights of 75%, 15%, and 10%, respectively.

The statistical event-by-event analysis of inelastic interactions of 16O and 32S nuclei in emulsion at 60 A GeV/c and 200 A GeV/c reveals the existence of groups of high multiplicity events belonging to very central nuclear interactions with Gaussian pseudorapidity distributions for produced particles as suggested by the original hydrodynamic-tube model. Characteristics of these events are presented. The experimental observations are interpreted as a result of quark-gluon plasma formation in the course of central nuclear interactions., 8 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1807.01234

The production of quark-gluon plasma is discussed within the hydrodynamic theory of multiparticle hadron production in head-on collisions of nucleons with nucleons and nuclei. In searches for collisions of a proton with a tube of a track-emulsion nucleus, the use of parametrically invariant quantities is proposed. An experimental verification of statistical models involving qualitatively different pseudorapidity distributions of weakly ionizing secondary particles is performed. The results of this verification are discussed.

A new method of an analysis of variances was developed for studying n-particle correlations of quasirapidities in nucleus-nucleus collisions for a large constant number n of particles. Formulas that generalize the results of the respective analysis to various values of n were derived. Calculations on the basis of simple models indicate that the method is applicable, at least for n ≥ 100. Quasirapidity correlations statistically significant at a level of 36 standard deviations were discovered in collisions between gold nuclei and track-emulsion nuclei at an energy of 10.6 GeV per nucleon. The experimental data obtained in our present study are contrasted against the theory of nucleus-nucleus collisions.

A method of parametrically invariant quantities is developed for studying pseudorapidity configurations in nucleus-nucleus collisions involving a large number of secondary particles. In simple models where the spectrum of pseudorapidities depends on three parameters, the shape of the spectrum may differ strongly from the shape of pseudorapidity configurations in individual events. Pseudorapidity configurations in collisions between gold nuclei of energy 10.6 GeV per nucleon and track-emulsion nuclei are contrasted against those in random stars calculated theoretically. An investigation of pseudorapidity configurations in individual events is an efficient method for verifying theoretical models.

Charged secondaries from collisions of gold nuclei with track-emulsion nuclei showed azimuthal correlations consisting in (i) the asymmetric emission of projectile and target fragments in opposite directions and (ii) an azimuthal quasicollinearity of shower particles in individual events. The measurement errors were investigated and taken into account. The experimental data in question can be interpreted within the model of Gaussian distributions of transverse momentum components.

Intra-and intergroup azimuthal correlations of projectile and target fragments are found in collisions between gold and emulsion nuclei. The statistical significance of these correlations is high. The methodological distortions associated with the measurement errors are investigated in detail and are taken into account.

A phenomenological analysis of the channels of the production of three and four alpha particles in 16Op collisions at 3.25 GeV/c per nucleon is performed for the first time under conditions of 4π geometry. The experimentally observed azimuthal asymmetries and collinearity are described on the basis of a phenomenological model that assumes that the excitation of the nucleus involved is peripheral and that its decay is statistical. It is shown that the azimuthal asymmetries in question are due to the transverse motion of the fragmenting nucleus. The mean transverse momentum of alpha particles and the collinearity of their emission in the reaction plane are found to be independent of the transverse-momentum transfer to the nucleus involved.

Phenomenological analysis of breakup of oxygen nuclei on fragments with the charges one and seven in collisions with protons at 3.25[Formula: see text][Formula: see text]GeV/[Formula: see text] was conducted using the Monte Carlo model of isotropic phase space. For the first time, the contributions of mechanism of diffractive breakup of oxygen nucleus and that of quasi-elastic knocking out of one of the protons of oxygen nucleus by a proton target into channel of formation of proton fragment and [Formula: see text]N nucleus with conservation of recoil proton in final state were determined. Cross-section of diffractive breakup of oxygen [Formula: see text]O nucleus on [Formula: see text]N nucleus and proton fragment and that of diffractive breakup of [Formula: see text]O nucleus on nuclei [Formula: see text]N and 2H were estimated for the first time in [Formula: see text]O[Formula: see text] collisions at 3.25[Formula: see text][Formula: see text]GeV/[Formula: see text].

Phenomenological analysis of breakup of oxygen nuclei on fragments with charges two and six in collisions with protons at [Formula: see text][Formula: see text]GeV/[Formula: see text] was conducted using the Monte Carlo (MC) model of isotropic phase space. For the first time, the contributions of mechanism of diffractive breakup of oxygen nucleus, and that of quasi elastic knocking out of one of the [Formula: see text] clusters of oxygen nucleus by a proton target, into channel of formation of [Formula: see text] particle and [Formula: see text]C nucleus with conservation of recoil proton were determined in final state. The substantial role of [Formula: see text] cluster structure of initial nucleus in processes of fragmentation of oxygen nuclei in peripheral interactions with protons was revealed in experiment.

Phenomenological Monte Carlo model of peripheral interactions of 9Be nuclei with emulsion nuclei at [Formula: see text][Formula: see text]GeV with formation of an excited 9Be* nucleus and its subsequent breakup, either directly or through formation of an intermediate 8Be nucleus, into two [Formula: see text]-particles and a neutron was constructed. A comparative analysis of the experimental data on angular correlations and momentum spectra of [Formula: see text]-particles, coming from a breakup event, with the Monte Carlo model calculations was made. The constructed Monte Carlo model described quite satisfactory the total momentum and transverse momentum distributions of [Formula: see text]-particles and the distribution of angles between the total momentum (as well as transverse momentum) vectors of two [Formula: see text]-particles in 9Be* nucleus breakup events in experiment. For the first time, the total momentum and transverse momentum distributions of neutrons, accompanying two [Formula: see text]-particles from 9Be* decay, in peripheral interactions of 9Be nuclei with emulsion nuclei were reconstructed using the Monte Carlo model.

A new cascade model of string breaking with 6 free parameters is constructed. The dual parton model of inelasticpp-collisions, which uses the supposed model of breaking of string, agrees well with the wide set of the experimental data at ISR energies, including the multiplicity, rapidity and transverse momentum distributions, the different correlations and the production cross sections of baryons, antibaryons, strange particles and resonances. For the fitted values of the free parameters, the scaling functions of the model of string breaking are similar to the hadron structure functions. The inability of the dual parton model to explain the rise of the average transverse momentum with multiplicity at the SPS collider energies is discussed.

By the methods of mathematical statistics we test a qualitative prediction of the old theory of relativistic hy-drodynamics non-viscous liquid which can be used as a part of the process of hadronization within the modern hydrody-namical approach for the description of the quark-gluon plasma. Experimental data on the interaction of protons with the energies of 0.8 TeV with emulsion nuclei are used. Results do not contradict the formation of relativistic ideal non-viscous liquid in rare central collisions.