Sudden freeze-out vs continuous emission: duality in hydro-kinetic approach to A+A collisions

The problem of spectra formation in hydrodynamic approach to A+A collisions is discussed. It is analyzed in terms of the two different objects: distribution and emission functions. We show that though the process of particle liberation, described by the emission function, is, usually, continuous in time, the observable spectra can be also expressed by means of the Landau/Cooper-Frye prescription. We argue that such an approximate duality results from some symmetry properties that systems in A+A collisions reach to the end of hydrodynamic evolution and reduction of the collision rate at post hydrodynamic stageComment: 6 pages, talk presented by S.V. Akkelin during the 3rd Budapest Winter School on Heavy Ion Physics, Dec. 8-11, 2003, Budapest, Hungar

Tubular initial conditions and ridge formation

The 2D azimuth & rapidity structure of the two-particle correlations in relativistic A+A collisions is altered significantly by the presence of sharp inhomogeneities in superdense matter formed in such processes. The causality constraints enforce one to associate the long-range longitudinal correlations observed in a narrow angular interval, the so-called (soft) ridge, with peculiarities of the initial conditions of collision process. This study's objective is to analyze whether multiform initial tubular structures, undergoing the subsequent hydrodynamic evolution and gradual decoupling, can form the soft ridges. Motivated by the flux-tube scenarios, the initial energy density distribution contains the different numbers of high density tube-like boost-invariant inclusions that form a bumpy structure in the transverse plane. The influence of various structures of such initial conditions in the most central A+A events on the collective evolution of matter, resulting spectra, angular particle correlations and v_n-coefficients is studied in the framework of the HydroKinetic Model (HKM).Comment: 18 pages, 6 figures, the paper to be published in Advances of High Energy Physics (2013, in press

Hydrokinetic predictions for femtoscopy scales in A+A collisions in the light of recent ALICE LHC results

A study of energy behavior of the pion spectra and interferometry scales is carried out for the top SPS, RHIC and for LHC energies within the hydrokinetic approach. The main mechanisms that lead to the paradoxical, at first sight, dependence of the interferometry scales with an energy growth, in particular, a decrease $R_{out}/R_{side}$ ratio, are exposed. The hydrokinetic predictions for the HBT radii at LHC energies are compared with the recent results of the ALICE experiment.Comment: Based on the talks given at the Sixth Workshop on Particle Correlations and Femtoscopy, BITP, Kiev, September 14 - 18, 2010 and GSI/EMMI Seminar, January 14, 201

Fast hadron freeze-out generator, part II: noncentral collisions

The fast Monte Carlo procedure of hadron generation developed in our previous work is extended to describe noncentral collisions of nuclei. We consider different possibilities to introduce appropriate asymmetry of the freeze-out hyper-surface and flow velocity profile. For comparison with other models and experimental data we demonstrate the results based on the standard parametrizations of the hadron freeze-out hyper-surface and flow velocity profile assuming either a common chemical and thermal freeze-out or the chemically frozen evolution from chemical to thermal freeze-out. The C++ generator code is written under the ROOT framework and is available for public use at http://uhkm.jinr.ru/Comment: 27 pages including 7 figures as EPS-files; prepared using LaTeX package for publication in Physical Review

Measurement of shower development and its Moli\`ere radius with a four-plane LumiCal test set-up

A prototype of a luminometer, designed for a future e+e- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Moli\`ere radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation.Comment: Paper published in Eur. Phys. J., includes 25 figures and 3 Table