Transverse-Mass Effective Temperature in Heavy-Ion Collisions from AGS to SPS

Transverse-mass spectra in Au+Au and Pb+Pb collisions in incident energy range from 2A to 160A GeV are analyzed within the model of 3-fluid dynamics. It is shown that dynamical description of freeze-out, accepted in this model, naturally explains the incident energy behavior of inverse-slope parameters of these spectra observed in experiment. Simultaneous reproduction of the inverse-slopes of all considered particles (protons, pions and kaons) suggests that these particles belong to the same hydrodynamic flow at the instant of their freeze-out.Comment: 4 pages, 3 figure

Dynamical Freeze-out in 3-Fluid Hydrodynamics

Freeze-out procedure accepted in the model of 3-fluid dynamics (3FD) is analyzed. This procedure is formulated in terms of drain terms in hydrodynamic equations. Dynamics of the freeze-out is illustrated by 1-dimensional simulations. It is demonstrated that the resulting freeze-out reveals a nontrivial dynamics depending on initial conditions in the expanding ``fireball''. The freeze-out front is not defined just ``geometrically'' on the condition of the freeze-out criterion met but rather is a subject the fluid evolution. It competes with the fluid flow and not always reaches the place where the freeze-out criterion is met. Dynamics of the freeze-out in 3D simulations is analyzed. It is demonstrated that the late stage of central nuclear collisions at top SPS energies is of the form of three (two baryon-rich and one baryon-free) fireballs separated from each other.Comment: 16 pages, 11 figures. Version accepted to Phys. Rev.

Relativistic Heavy-Ion Collisions within 3-Fluid Hydrodynamics: Hadronic Scenario

A 3-fluid hydrodynamic model for simulating relativistic heavy-ion collisions is introduced. Alongside with two baryon-rich fluids, the new model considers time-delayed evolution of a third, baryon-free (i.e. with zero net baryonic charge) fluid of newly produced particles. Its evolution is delayed due to a formation time, during which the baryon-free fluid neither thermalizes nor interacts with the baryon-rich fluids. After the formation it starts to interact with the baryon-rich fluids and quickly gets thermalized. Within this model with pure hadronic equation of state, a systematic analysis of various observables at incident energies between few and about 160A GeV has been done as well as comparison with results of transport models. We have succeeded to reasonably reproduce a great body of experimental data in the incident energy range of E_{lab} = (1-160)A GeV. The list includes proton and pion rapidity distributions, proton transverse-mass spectra, rapidity distributions of Lambda and antiLambda hyperons, elliptic flow of protons and pions (with the exception of proton v2 at 40A GeV), multiplicities of pions, positive kaons, phi-mesons, hyperons and antihyperons, including multi-strange particles. This agreement is achieved on the expense of substantial enhancement of the interflow friction as compared to that estimated proceeding from hadronic free cross sections. However, we have also found out certain problems. The calculated yield of K^- is approximately by a factor of 1.5 higher than that in the experiment. We have also failed to describe directed transverse flow of protons and pion at E_{lab} > 40A GeV. This failure apparently indicates that the used EoS is too hard and thereby leaves room for a phase transition.Comment: 30 pages, 20 figures, 2 tables. Version accepted for publication in Phys. Rev.

National identity of the population in Chelyabinsk

В статье приводятся результаты исследования национальной идентичности жителей г. Челябинска. На основе эмпирического материала сравниваются основные виды идентичности четырех возрастных групп и анализируются выявленные различия гражданских и этнических установок респондентов.The article presents the data of sociological research devoted to the problem of national identity citize3nce of Chelyabinsk. The author compares main identities of four groups people of different ages, considers different attitudes of respondents ( civic, ethnic, religious, national)

Transverse-Mass Spectra in Heavy-Ion Collisions at energies E_{lab} = 2--160 GeV/nucleon

Transverse-mass spectra of protons, pions and kaons produced in collisions of heavy nuclei are analyzed within the model of 3-fluid dynamics. It was demonstrated that this model consistently reproduces these spectra in wide ranges of incident energies E_{lab}, from 4A GeV to 160A GeV, rapidity bins and centralities of the collisions. In particular, the model describes the "step-like" dependence of kaon inverse slopes on the incident energy. The key point of this explanation is interplay of hydrodynamic expansion of the system with its dynamical freeze-out.Comment: 13 pages, 16 figures, summary is extended, version accepted by Phys. Rev.

Production of radioactive isotopes in nuclear research reactor for experimental studies of the properties of homogeneous radiation-shielding materials

Приведено обоснование необходимости верификации результатов расчетного определения состава гомогенных радиационно-защитных материалов для планируемых условий облучения. Описана технология получения радиоактивных изотопов на исследовательском ядерном реакторе для экспериментального определения защитных свойств РЗМ. Приведены характеристики мишеней и полученных радиоактивных изотопов. Описана установка для проведения измерений кратности ослабления гамма-излучения радиоактивных источников образцами радиационно-защитных материалов.The substantiation of the need to verify the results of the calculation determination of homogeneous composition of radiation-shielding materials for the intended irradiation conditions. The technology of production of radioactive isotopes in the nuclear research reactor for the experimental determination of the protective properties of rare-earth metals is described. The characteristics of the targets and the produced radioactive isotopes are given. A facility for the measurement of multiplicity attenuation of gamma radiation from radioactive sources, samples of radiation-shielding materials is described

Continuous Decoupling of Dynamically Expanding Systems

The question of decoupling and freeze-out is reinvestigated and analysed in terms of transparent semi-classical decoupling formulae, which provide a smooth decoupling in time both, for single and two particle inclusive spectra. They generalise frequently employed instantaneous freeze-out procedures and provide simple relations between the damping width and the duration of the decoupling process. The implications on physical phenomena arising from the expansion and decay dynamics of the highly compressed hadronic matter generated in high energy nuclear collisions are discussed.Comment: The paper is significantly revised concentrating on the physics discussion, thereby including material that appeared during the revision stage. The formal derivations are deferred to a forthcoming paper. 20 pages, 2 Figures, Nucl. Phys. A in pres