Maciej Rybczynski

GLISSANDO: Glauber initial-state simulation and more..

Abstract We present a Monte Carlo generator for a variety of Glauber-like models (the wounded-nucleon model, binary collisions model, mixed model, model with hot spots). These models describe the early stages of relativistic heavy-ion collisions, in particular the spatial distribution of the transverse energy deposition which ultimately leads to production of particles from the interaction region. The original geometric distribution of sources in the transverse plane can be superimposed with a statistical distribution simulating the dispersion in the generated transverse energy in each individual collision. The program generates inter alia the fixed-axes (standard) and variable-axes (participant) two-dimensional profiles of the density of sources in the transverse plane and their azimuthal Fourier components. These profiles can be used in further analysis of physical phenomena, such as the jet quenching, event-by-event hydrodynamics, or analysis of the elliptic flow and its fluctuations. Characteristics of the event (multiplicities, eccentricities, Fourier coefficients, etc.) are stored in a ROOT file and can be analyzed off-line. In particular, event-by-event studies can be carried out in a simple way. A number of ROOT scripts is provided for that purpose. Supplied variants of the code can also be used for the proton–nucleus and deuteron–nucleus collisions. Program summary Program title: GLISSANDO Catalogue identifier: AEBS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBS_v1_0.html Program obtainable from: CPC Program Library, Queens University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4452 No. of bytes in distributed program, including test data, etc.: 34u2009766 Distribution format: tar.gz Programming language: C++ Computer: any computer with a C++ compiler and the ROOT environment [R. Brun, et al., Root Users Guide 5.16, CERN, 2007, http://root.cern.ch [1] ], tested with Intel Core 2 Duo T5200, 1.6 GHz, 1 GB RAM Operating system: Linux Ubuntu 7.04-8.04 (gcc 4.1.3-4.2.3), Scientific Linux CERN 3.08 (gcc 3.2.3), Windows XP with Cygwin (gcc 3.4.4 cygwin special), MacBook Pro OSX 10.5.2 (gcc 4.0.1), ROOT ver. 5.08 5.18 RAM: below 120 MB Classification: 17.8 External routines: The ROOT system [R. Brun, et al., Root Users Guide 5.16, CERN, 2007, http://root.cern.ch [1] ] Nature of problem: Glauber-like models of the initial state in relativistic heavy-ion collisions Solution method: Glauber Monte Carlo simulation of collision events, analyzed with ROOT Running time: 40 s/10u2009000 events for the wounded-nucleon model and 60 s/10u2009000 events for the mixed model with the Γ distribution, minimum-bias Auxa0+xa0Au collisions with the fixed-last algorithm for nuclear repulsion, dispersion of sources, and hardsphere wounding profile. a typical “physics” run with 500u2009000 events takes about 1 hour. The use of the Gaussian wounding profile increases the time about 6 times. (All times for Intel Core 2 Duo T5200 1.6 GHz) References: [1] R. Brun, et al., Root Users Guide 5.16, CERN, 2007, http://root.cern.ch

Fluctuating initial conditions in heavy ion collisions from the Glauber approach

In the framework of the Glauber approach applied to the initial stage of ultra-relativistic heavy-ion collisions we analyze the shape parameters of the early-formed system (fireball) and their event-by-event fluctuations. We test a variety of models: the conventional wounded-nucleon model, a model admixing binary collisions to the wounded nucleons, a model with hot spots, and the hot-spot model where the deposition of energy occurs with a superimposed probability distribution. We look in detail at the so-called participant harmonic moments, {epsilon}*, obtained by an averaging procedure where in each event the system is translated to its center of mass and aligned with the major principal axis of the ellipse of inertia. Quantitative comparisons indicate substantial relative effects for {epsilon}* in variants of Glauber models. However, the dependence of the scaled standard deviation {delta}{epsilon}*/, {epsilon}* on the chosen model is weak. For all models the values range from about 0.5 for the central collisions to about 0.3-0.4 for peripheral collisions, for both gold-gold and copper-copper collisions. They are dominated by statistics and change only by 10-15% from model to model. We provide an approximate analytic expansion for the harmonic moments and their fluctuations given in terms of the fixed-axes moments. For centralmorexa0» collisions and in the absence of correlations the expansion gives the simple formula {delta}{epsilon}*/{epsilon}*{approx_equal}{radical}(4/{pi}-1)=0.52. Similarly, we obtain expansions for the radial profiles of the higher harmonics. We investigate the relevance of the shape-fluctuation effects for jet quenching and find them important only for very central events. Finally, we make some comments of relevance for hydrodynamics, the elliptic flow, and its fluctuations. We argue how smooth hydrodynamics leads to the known result v{sub 4}{approx}v{sub 2}{sup 2} and, further, to the prediction {delta}v{sub 4}/v{sub 4}=2{delta}v{sub 2}/v{sub 2}.«xa0less

GLISSANDO 2: GLauber Initial-State Simulation AND mOre…, ver. 2☆☆☆

Abstract We present an extended version of GLISSANDO , a Monte-Carlo generator for Glauber-like models of the initial stage of relativistic heavy-ion collisions. The increased functionality of the code incorporates a parametrization of shape of nuclei, including light nuclei needed in the NA61 experiment, the nuclear deformation, a possibility of using correlated distributions of nucleons in nuclei read from external files, an option of overlaying distributions of produced particles dependent on the space–time rapidity, the inclusion of the core–corona effect, or the output of the source distributions that can be used in event-by-event hydrodynamics. Together with other features, such as incorporation of various variants of Glauber models, or the implementation of a realistic NN collision profile, the generator offers a realistic and practical approach to describe the early phase of the collision in 3 + 1 dimensions; the predictions may later be used in modeling the intermediate evolution phase, e.g., with hydrodynamics. The software is integrated with the ROOT platform. The supplied scripts compute and plot numerous features of the distributions, such as the multiplicity distributions and centrality classes, harmonic asymmetry coefficients and their correlations, forward–backward correlations, etc. The code can also be used for the proton–nucleus and deuteron–nucleus collisions. Program summary Program title: GLISSANDO 2 ver. 2.702 Catalog identifier: AEBS_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBS_v2_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC license, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 41067 No. of bytes in distributed program, including test data, etc.: 454358 Distribution format: tar.gz Programming language: C++ with the ROOT libraries. Computer: Any computer with a C++ compiler and the ROOT environment (optionally with doxygen), tested with Intel Xeon X5650, 2.67 GHz, 2 GB RAM. Operating system: Linux Ubuntu 7.04-12.04 (gcc 4.1.3-4.6.3), Scientific Linux CERN 5.10 (gcc 4.1.2), ROOT ver. 5.28-5.34/09. RAM: Below 120 MB Classification: 17.8. Catalog identifier of previous version: AEBS_v1_0 Journal reference of previous version: Comput. Phys. Comm. 180(2009)69 External routines: ROOT ( http://root.cern.ch/drupal/ ) Does the new version supersede the previous version?: Yes, however the functionality of GLISSANDO 2 and the format of the input and output files is down-compatible with the original version. Nature of problem: Glauber models of the initial state in relativistic heavy-ion collisions. Solution method: Glauber Monte-Carlo simulation of collision events, analyzed with ROOT. Reasons for new version: This is an updated and largely enhanced version of the program GLISSANDO. The structure of the C++ code has been simplified and the organization of the package is restructured. Summary of revisions: The new features implemented in GLISSANDO 2 include: • Parametrization of shape of all typical nuclei, including light nuclei. This is useful in applications for the NA61 experiment, where the mass-number scan will be carried out. • Inclusion of the deformation of the colliding nuclei. In particular, the deformation effects are relevant for the collisions involving the deformed Au and U nuclei recently used at RHIC. • Possibility of using correlated distributions of nucleons in nuclei, which may be read-in from external files prepared earlier with other codes. Certainly, the two-body correlations are important, as they influence the fluctuations. • Generalization of the NN collision profile a shape which interpolates between the step function and a Gaussian profile. Such an extension is relevant for the collisions at the LHC energies, allowing reproduction of the measured values of both the total and elastic NN cross sections. • Inclusion of the negative binomial overlaid distribution (in addition to the Poissonian and Gamma distributions). • Possibility of overlaying distributions of the produced particles which depend on the space–time rapidity. This feature extends the model into a fully 3 + 1 dimensional tool. • Inclusion of the core–corona effect. • A doxygen-generated reference manual is available, which is useful for those who wish to alter the code for their needs. Additional comments: Optional software—doxygen ( http://www.stack.nl/dimitri/doxygen/ ) Running time: 80xa0s/10,000 events for the wounded-nucleon model and 100xa0s/10,000 events for the mixed model with the Γ distribution, minimum-bias Pb+Pb collisions and hard-sphere wounding profile. A typical high-statistics “physics” run with 500,000 events takes about 1xa0h. The use of the Gaussian wounding profile increases the time by about a factor of 2. (All times for Intel Xeon X5650, 2.67xa0GHz, 2xa0GB RAM.)

Tsallis statistics approach to the transverse momentum distributions in p–p collisions

Transverse momentum distributions of negatively charged pions produced in p–p interactions at beam momenta 20, 31, 40, 80, and 158xa0GeV

Rapidity spectra analysis in terms of non-extensive statistic approach

/c

Transverse-momentum spectra of strange particles produced in Pb+Pb collisions at

/c are studied using the Tsallis distribution as a parametrization. Results are compared with higher energy data and changes of parameters with energy are determined. Different Tsallis-like distributions are compared.

\sqrt{s_{\rm NN}}=2.76

Results are presented on event-by-event fluctuations in transverse momentum of charged particles, produced at forward rapidities in p+p, C+C, Si+Si and Pb+Pb collisions at 158 AGeV. Three different characteristics are discussed: the average transverse momentum of the event, the Phi_pT fluctuation measure and two-particle transverse momentum correlations. In the kinematic region explored, the dynamical fluctuations are found to be small. However, a significant system size dependence of Phi_pT is observed, with the largest value measured in peripheral Pb+Pb interactions. The data are compared with predictions of several models.

TeV in the chemical non-equilibrium model

We provide the description of rapidity spectra of particles produced in pp collisions using the anomalous diffusion approach to account for their non-equilibrium character. In particular, we exhibit connections between multiproduction processes and anomalous diffusion described through the nonlinear Focker-Planck equation with a nonlinearity given by the nonextensivity parameter q describing the underlying Tsallis q-statistics. We demonstrate how this leads to the Feynman scaling violation in these collisions. The q parameter obtained in this way turns out to be closely connected to the parameter 1k converting the original poissonian multiplicity distribution to its observed Negative Binomial form. The inelasticity of the reaction has also been calculated and found to slightly decrease with increasing reaction energy.Abstract We provide the description of rapidity spectra of particles produced in pp collisions using the anomalous diffusion approach to account for their non-equilibrium character. In particular, we exhibit connections between multiproduction processes and anomalous diffusion described through the nonlinear Focker-Planck equation with a nonlinearity given by the nonextensivity parameter q describing the underlying Tsallis q-statistics. We demonstrate how this leads to the Feynman scaling violation in these collisions. The q parameter obtained in this way turns out to be closely connected to the parameter 1 k converting the original poissonian multiplicity distribution to its observed Negative Binomial form. The inelasticity of the reaction has also been calculated and found to slightly decrease with increasing reaction energy.