arXiv subjects

Wojciech Florkowski

Publications and source records attributed to Wojciech Florkowski.

At least 145 records · Page 8Linked to original sources

arXiv2006

Femtoscopy in hydro-inspired models with resonances

Effects of the choice of the freeze-out hypersurface and resonance decays on the HBT interferometry in relativistic heavy-ion collisions are studied in detail within a class of models with single freeze-out. The Monte-Carlo method, as implemented in THERMINATOR, is used to generate hadronic events describing production of particles from a thermalized and expanding source. All well-established hadronic resonances are included in the analysis as their role is crucial at large freeze-out temperatures. We use the two-particle method to extract the correlation functions, which allows us to study the Coulomb effects. We find that the pion HBT data from RHIC are fully compatible with the single freeze-out scenario, pointing at the shape of the freeze-out hypersurface where the transverse radius is decreasing with time. Results for the single-particle spectra for this situation are also presented. Finally, we present predictions for the kaon femtoscopy.

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arXiv2005

Particle spectra and hydro-inspired models

Several popular parameterizations of the freeze-out conditions in ultra-relativistic heavy-ion collisions are shortly reviewed. The common features of the models, responsible for the successful description of hadronic observables, are outlined.

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arXiv2005

Therminator: Thermal heavy-Ion generator

THERMINATOR is a Monte Carlo event generator designed for studying of particle production in relativistic heavy-ion collisions performed at such experimental facilities as the SPS, RHIC, or LHC. The program implements thermal models of particle production with single freeze-out. It performs the following tasks: 1) generation of stable particles and unstable resonances at the chosen freeze-out hypersurface with the local phase-space density of particles given by the statistical distribution factors, 2) subsequent space-time evolution and decays of hadronic resonances in cascades, 3) calculation of the transverse-momentum spectra and numerous other observables related to the space-time evolution. The geometry of the freeze-out hypersurface and the collective velocity of expansion may be chosen from two successful models, the Cracow single-freeze-out model and the Blast-Wave model. All particles from the Particle Data Tables are used. Experimental cuts may be introduced in a very straightforward manner. The code is written in the object-oriented c++ language and complies to the standards of the ROOT environment.

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arXiv2004

Hydro-inspired parameterizations of freeze-out in relativistic heavy-ion collisions

Popular parameterizations of the freeze-out conditions in relativistic heavy-ion collisions are discussed. Similarities and differences between the blast-wave model and the single-freeze-out model, both used recently to interpret the RHIC data, are outlined. A non-boost-invariant extension of the single-freeze-out model is proposed and applied to describe the recent BRAHMS data.

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arXiv2004

On the formation of Hubble flow in Little Bangs

A dynamical appearance of scaling solutions in the relativistic hydrodynamics applied to describe ultra-relativistic heavy-ion collisions is studied. We consider the boost-invariant cylindrically symmetric systems and the effects of the phase transition are taken into account by using a temperature dependent sound velocity inferred from the lattice simulations of QCD. We find that the transverse flow acquires the scaling form r/t within the short evolution times, 10 - 15 fm, only if the initial transverse flow originating from the pre-equilibrium collective behavior is present at the initial stage of the hydrodynamic evolution. The amount of such pre-equilibrium flow is correlated with the initial pressure gradient; larger gradients require smaller initial flow. The results of the numerical calculations support the phenomenological parameterizations used in the Blast-Wave, Buda-Lund, and Cracow models of the freeze-out process.

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arXiv2004

Update of the Hagedorn mass spectrum

We present an update of the Hagedorn hypothesis of the exponential growth of the number of hadronic resonances with mass. We use the newest available experimental data for the non-strange mesons and baryons, as well as fill in some missing states according to the observation that the high-lying states form chiral multiplets. The results show, especially for the case of the mesons, that the Hagedorn growth continues with the increasing mass, with the new states lining up along the exponential growth.

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arXiv2004

SHARE: Statistical Hadronization with Resonances

SHARE is a collection of programs designed for the statistical analysis of particle production in relativistic heavy-ion collisions. With the physical input of intensive statistical parameters, it generates the ratios of particle abundances. The program includes cascade decays of all confirmed resonances from the Particle Data Tables. The complete treatment of these resonances has been known to be a crucial factor behind the success of the statistical approach. An optional feature implemented is a Breit--Wigner type distribution for strong resonances. An interface for fitting the parameters of the model to the experimental data is provided.

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arXiv2004

Production of resonances in a thermal model

We discuss the pi+ pi- invariant-mass correlations and the resonance production in a thermal model with single freeze-out. The predictions are confronted with the data from the STAR Collaboration.

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arXiv2003

Resonance production in a thermal model

We discuss the pi+ pi- invariant-mass correlations and the resonance production in a thermal model with single freeze-out. The predictions are confronted with the recent data from the STAR Collaboration.

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arXiv2003

Schwinger tunneling and thermal character of hadron spectra

It is shown that an oscillatory character of the solutions of the collisionless kinetic equations describing production of the quark-gluon plasma in strong color fields leads to the exponential (thermal-like) transverse-momentum spectra of partons produced in the soft region (100 MeV < pt < 1 GeV). In addition, the production of partons in the very soft region (pt < 100 MeV) is clearly enhanced above the thermal-like background.

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arXiv2003

Thermal analysis of production of resonances in relativistic heavy-ion collisions

Production of resonances is considered in the framework of the single-freeze-out model of ultra-relativistic heavy ion collisions. The formalism involves the virial expansion, where the probability to form a resonance in a two-body channel is proportional to the derivative of the phase-shift with respect to the invariant mass. The thermal model incorporates longitudinal and transverse flow, as well as kinematic cuts of the STAR experiment at RHIC. We find that the shape of the pi+ pi- spectral line qualitatively reproduces the preliminary experimental data when the position of the rho peak is lowered. This confirms the need to include the medium effects in the description of the RHIC data. We also analyze the transverse-momentum spectra of rho, K*(892), and f_0(980), and find that the slopes agree with the observed values. Predictions are made for eta, eta', omega, phi, Lambda(1520), and Sigma(1385).

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arXiv2002

Thermal model for RHIC, part I: particle ratios and spectra

A simple thermal model with single freeze-out and flow is used to analyze the ratios of hadron yields and the hadron transverse-mass spectra measured in 130 GeV Au+Au collisions at RHIC. An overall very good agreement between the model predictions and the data is achieved for all measured hadron species, including hyperons.

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arXiv2002

Thermal model at RHIC, part II: elliptic flow and HBT radii

We continue the analysis of the preceding talk with a discussion of the elliptic flow and the HBT pion correlation radii. It is shown that the thermal model can be extended to describe these phenomena. The description of the elliptic flow involves an appropriate deformation of the freeze-out hypersurface and flow velocity. The obtained results agree reasonably with the data for soft (< 2 GeV) transverse momenta. For the pionic HBT correlation radii the experimental feature that R_out/R_side ~ 1 is naturally obtained. The reproduction of individual R_side and R_out can be achieved with the inclusion of the excluded volume corrections, which effectively increase the radii by \~30%.

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arXiv2002

Thermal approach to RHIC

Applications of a simple thermal model to ultra-relativistic heavy-ion collisions are presented. We compute abundances of various hadrons, including particles with strange quarks, the pT-spectra, and the HBT radii for the pion. Surprising agreement is found, showing that the thermal approach can be used successfully to understand and describe the RHIC data.

hep-ph↗

arXiv2002

Thermal description of transverse-momentum spectra at RHIC

We show that the transverse-momentum spectra of all hadrons measured at RHIC, including hyperons, are described very well in a thermal model assuming the simultaneous chemical and thermal freeze-outs. The model calculation takes into account all hadronic resonances and uses a simple parametrization of the freeze-out hypersurface.

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arXiv2002

How much is RHIC different from SPS? Comparison of the pT-spectra

We show, by means of a simple compilation of the available experimental results, that the pT-spectra obtained at RHIC and SPS are strikingly similar up to pT ~ 1.5-2 GeV. In fact, the discrepancies between various experimental groups working at the same experiment are of the same size as the differences between RHIC and SPS. Our observation is complementary to the well known fact of the equality of the measured R_side and R_out HBT radii at RHIC and SPS. In essence, it points out that the transverse size of the firecylinder and the strength of the transverse flow are not significantly changed between SPS and RHIC. This suggests that a saturation mechanism is effective already at SPS. We also point out that the dominance of protons over pi^+ at large pT can be seen not only in the RHIC data, but already in the SPS data.

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arXiv2002

Strange particle production at RHIC in a single-freeze-out model

Strange particle ratios and pT-spectra are calculated in a thermal model with single freeze-out, previously used successfully to describe non-strange particle production at RHIC. The model and the recently released data for phi, Lambda, anti-Lambda, and K*(892) are in very satisfactory agreement, showing that the thermal approach can be used to describe the strangeness production at RHIC.

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arXiv2002

Explanation of the RHIC pt-spectra in a single-freeze-out model

The pt-spectra of hadrons measured at RHIC are very well described in a model which assumes that the chemical and thermal freeze-outs occur simultaneously. The model calculation includes all hadronic resonances and uses a simple parametrization of the freeze-out hypersurface.

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