The effect of a fluctuating bumping structure of the initial conditions on spectra and the collective evolution of matter created in heavy-ion collisions in the frameworks of the Hydro-Kinetic Model is investigated. As moti-vated by the glasma-flux-tube scenario, the initial conditions are modeled by the set of four high energy-density tube-like fluctuations with longitudinally homogeneous structure within some space-rapidity region in a boost-invariant 2D geometry. It was found that the presence of transversally bumping tube-like fluctuations in initial conditions strongly affects the hydrodynamic evolution and leads to emergence of conspicuous structures in the calculated pion spectra. It was observed that the 4 tube initial configuration generates a four-peak structure in the final azimuthal distributions of one-particle spectra.
The analysis of particle correlations as a function of relative pseudo-rapidity and azimuthal angle exhibit novel ridge-like structures that were discovered at RHIC in A + A collisions. Such an analysis is of great interest for forthcoming ALICE LHC experiment. This structure which is unusually wide in the longitudinal direction remains after removal of the known correlation-inducing effects such as elliptic flow and ordinary jet correlations. It could be probably explained only if one supposes that the ridge phenomenon in relativistic A + A collisions is rooted in the initial conditions of the thermal evolution of the system. The aim of this study is to check this hypothesis by an analysis of the evolution of the energy density in the system which at very initial stage of collisions has high density tube-like fluctuations with boost-invariant longitudinally homogeneous structure within some space-rapidity region. The transverse-velocity and energy density profiles, which develop in the system when it reaches the chemical freeze-out (T = 165 MeV) for different initial configurations at t 0 = 0.2 fm/c, are considered.
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 funetions. 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 stage.
Two-particle angular correlation for charged particles emitted in Au+Aucollisions at the center-of-mass of 200 MeV measured at RHIC energies revealednovel structures commonly referred to as a near-side ridge. The ridgephenomenon in relativistic A+A collisions is rooted probably in the initialconditions of the thermal evolution of the system. In this study we analyze theevolution of the bumping transverse structure of the energy densitydistribution caused by fluctuations of the initial density distributions thatcould lead to the ridge structures. We suppose that at very initial stage ofcollisions the typical one-event structure of the initial energy densityprofile can be presented as the set of longitudinal tubes, which areboost-invariant in some space-rapidity region and are rather thin. These tubeshave very high energy density comparing to smooth background densitydistribution. The transverse velocity and energy density profiles at differenttimes of the evolution till the chemical freeze-out (at the temperature T=165MeV) willbe reached by the system are calculated for sundry initial scenarios.
The 2D azimuth and 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 studys 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 vn-coefficients is studied in the framework of the hydrokinetic model (HKM).
Design of STS and module prototype of silicon micro-strip detector for particle momenta measurements with a resolution of around Δp/p ≈ 1 % are presented. Very high radiation level and inhomogeneous track distribution result in modular construction of the detector stations. The micro-strip detectors are planned to be read out with the help of СВМ-XYTER chip. The system requirements include radiation tolerant sensors with high spatial resolution and a fast readout compatible with high-level-only triggers. Concept of the silicon detection system and the R&D on micro-strip sensors as well as front-end electronics for the building blocks of the detector stations are discussed.