Statistical Hadronization Model Research Articles

Charmonium and open charm production in nuclear collisions at SPS/FAIR energies and the possible influence of a hot hadronic medium

We provide predictions for charmonium and open charm production in nuclear collisions at SPS/FAIR energies within the framework of the statistical hadronization model. The increasing importance at lower energies of Λc production is demonstrated and provides a challenge for future experiments. We also demonstrate that, because of the large charm quark mass and the different timescales for charm quark and charmed hadron production, possible modifications of charmed hadrons in the hot hadronic medium do not lead to measurable changes in cross sections for D-meson production. A possible influence of medium effects can be seen, however, in yields of charmonium. These effects are visible at all energies and results are presented for the energy range between charm threshold and RHIC energy.

A STATISTICAL MODEL ANALYSIS OF K/π FLUCTUATIONS IN HEAVY ION COLLISIONS

We briefly describe two statistical hadronization models, based respectively on the presence and absence of light quark chemical equilibrium, used to analyze particle yields in heavy ion collisions. We then try to distinguish between these models using K/π fluctuations data. We find that while the non-equilibrium model provides an acceptable description of fluctuations at top SPS and RHIC energies, both models considerably under-estimate fluctuations at low SPS energies.

Evidence for charmonium generation at the phase boundary in ultra-relativistic nuclear collisions

We investigate the transition from suppression to enhancement of J/ψ mesons produced in ultra-relativistic nuclear collisions in the framework of the statistical hadronization model. The calculations are confronted with the most recent data from the RHIC accelerator. This comparison yields first direct evidence for generation of J/ψ mesons at the phase boundary. Based on the success of this approach we make specific predictions for LHC energy.

Quarkonium production in ultra-relativistic nuclear collisions: suppression versus enhancement

After a brief review of the various scenarios for quarkonium production in ultra-relativistic nucleus–nucleus collisions, we focus on the ingredients and assumptions underlying the statistical hadronization model. We then confront model predictions for J/ψ phase space distributions with the most recent data from the RHIC accelerator. Analysis of the rapidity dependence of the J/ψ nuclear modification factor yields first evidence for the production of J/ψ mesons at the phase boundary. We conclude with predictions for charmonium production at the LHC.

Heavy flavor hadrons in statistical hadronization of strangeness-rich QGP

We study b and c quark hadronization from QGP. We obtain the yields of charm and bottom flavored hadrons within the statistical hadronization model. The important novel feature of this study is that we take into account the high strangeness and entropy content of QGP, conserving the strangeness and entropy yields at hadronization.

Statistical hadronization model approach tosNN=200GeV Au-Au collisions:pT-spectra fits and global variable predictions

Three possible scenarios of the statistical hadronization model are reexamined with the use of the p{sub T} spectra of the PHENIX and very low p{sub T} PHOBOS measurements at {radical}(s{sub NN})=200 GeV. These scenarios are as follows: (a) full chemical nonequilibrium, (b) strangeness chemical nonequilibrium, and (c) chemical equilibrium. Fits to the spectra are done within the Cracow single-freeze-out model, which takes into account both the expansion and resonance decays. Predictions for spectra of {phi},K(892){sup *0}, and {pi}{sup 0} are also given. Global variables such as the transverse energy at midrapidity, the charged particle multiplicity at midrapidity, and the total multiplicity of charged particles are evaluated and their predicted values agree qualitatively well with the experimental data. The thorough analysis within this model suggests that the chemical full nonequilibrium case is the least likely and both other cases are of similar likelihood. It is also shown that if the full chemical nonequilibrium freeze-out took place it could manifest itself in the enhancement of the {pi}{sup 0} production at very low transverse momenta.

Resonances and fluctuations of strange particles in 200 GeV Au–Au collisions

We perform an analysis of preliminary data on strange particles yields and fluctuations within the statistical hadronization model. We begin by describing the theoretical disagreements between different statistical models currently on the market. We then show how the simultaneous analysis of yields and fluctuations can be used to differentiate between the different models, and determine if one of them can be connected to underlying physics. We perform a study on a RHIC 200 GeV data sample that includes stable particles, resonances and the event-by-event fluctuation of the K/π ratio. We show that the equilibrium statistical model cannot describe the fluctuation, unless an unrealistically small volume is assumed. Such a small volume then makes it impossible to describe the total particle multiplicity. The non-equilibrium model, on the other hand, describes both the K/π fluctuation and yields acceptably due to the extra boost to the π fluctuation provided by the high-pion chemical potential. Λ(1520) and K* abundance is described within error bars, but the Σ* is under-predicted to ∼1.5 standard deviations. We suggest further measurements that have the potential to test the non-equilibrium model, as well as gauge the effect of re-interactions between hadronization and freeze-out.

Charmed hadrons from strangeness-rich QGP

The yields of charmed hadrons emitted by strangeness-rich QGP are evaluated within the chemical non-equilibrium statistical hadronization model, conserving strangeness, charm and entropy yields at hadronization.

J/Ψ measurements in Au + Au and p + p collisions at

In a system of deconfined quarks and gluons heavy quarkonium states are expected to be the subject of dissociation via static mechanisms such as colour screening or dynamic mechanisms such as gluon scatterings. This leads to a suppression of hidden charm states, such as J/ψ. On the other hand, statistical hadronization models predict an enhanced production of hidden charm states for sufficiently high charm densities. We present first preliminary STAR results on J/ψ production via the reconstruction of electron–positron decay pairs in p + p and Au + Au collisions at . The implications of our measurements to models that predict copious J/ψ production via statistical hadronization are discussed.

SHAREv2: fluctuations and a comprehensive treatment of decay feed-down

This the user’s manual for SHARE version 2. SHARE [G. Torrieri, S. Steinke, W. Broniowski, W. Florkowski, J. Letessier, J. Rafelski, Comput. Phys. Comm. 167 (2005) 229] (Statistical Hadronization with Resonances) is a collection of programs designed for the statistical analysis of particle production in relativistic heavy-ion collisions. While the structure of the program remains similar to v1.x, v2 provides several new features such as evaluation of statistical fluctuations of particle yields, and a greater versatility, in particular regarding decay feed-down and input/output structure. This article describes all the new features, with emphasis on statistical fluctuations. Program summary

Particle yield fluctuations and chemical nonequilibrium in Au-Au collisions atsNN=200GeV

We study charge fluctuations within the statistical hadronization model. Considering both the particle yield ratios and the charge fluctuations we show that it is possible to differentiate between chemical equilibrium and non-equilibrium freeze-out conditions. As an example of the procedure we show quantitatively how the relative yield ratio $\ensuremath{\Lambda}/{K}^{\ensuremath{-}}$ together with the normalized net charge fluctuation $v(Q)=\ensuremath{\langle}(\ensuremath{\Delta}Q){}^{2}\ensuremath{\rangle}/\ensuremath{\langle}{N}_{\mathrm{ch}}\ensuremath{\rangle}$ constrain the chemical conditions at freeze-out. We also discuss the influence of the limited detector acceptance on fluctuation measurements, and show how this can be accounted for within a quantitative analysis.

Energy and system size dependence of chemical freeze-out in relativistic nuclear collisions

We present a detailed study of chemical freeze-out in p-p, C-C, Si-Si and Pb-Pb collisions at beam momenta of 158A GeV as well as Pb-Pb collisions at beam momenta of 20A, 30A, 40A and 80A GeV. By analyzing hadronic multiplicities within the statistical hadronization model, we have studied the parameters of the source as a function of the number of the participating nucleons and the beam energy. We observe a nice smooth behaviour of temperature, baryon chemical potential and strangeness under-saturation parameter as a function of energy and nucleus size. Interpolating formulas are provided which allow to predict the chemical freeze-out parameters in central collisions at centre-of-mass energies > 4.5 GeV and for any colliding ions. Specific discrepancies between data and model emerge in particle ratios in Pb-Pb collisions at SPS between 20A and 40A GeV of beam energy which cannot be accounted for in the considered model schemes.

Soft hadron ratios at the LHC

High precision soft hadron abundance data produced in relativistic nuclear collisions at LHC at $\sqrt{s_{\rm NN}}\le 5500$ GeV will become available beginning in 2007/8. We explore, within the statistical hadronization model, how these results can help us understand the properties of the deconfined quark--gluon phase at its breakup. We make assumptions about the physical properties of the fireball and obtain particle production predictions. Then, we develop a strategy to measure parameters of interest, such as strangeness occupancy $\gamma_s$, chemical potentials $\mu_{\rm B}$ and $\mu_{\rm S}$.

Centrality dependence of bulk fireball properties insNN=200GeVAu–Au collisions

We explore the centrality dependence of the properties of the dense hadronic matter created in $\sqrt{{s}_{\mathit{NN}}}=200$ GeV Au-Au collisions at the Relativistic Heavy Ion Collider. Using the statistical hadronization model, we fit particle yields known for 11 centrality bins. We present the resulting model parameters, rapidity yields of physical quantities, and the physical properties of bulk matter at hadronization as function of centrality. We discuss the production of strangeness and entropy.

Heavy flavour probes of quark matter

A brief survey of the role of heavy flavours as a probe of the state of matter produced by high-energy heavy-ion collisions is presented. Specific examples include energy loss, initial-state gluon saturation, thermalization and flow. The formation of quarkonium bound states from interactions in which multiple heavy–quark-antiquark pairs are initially produced is examined in general. Results from statistical hadronization and kinetic models are summarized. New predictions from the kinetic model for J/ψ at RHIC are presented.

Chemical equilibrium study at SPS 158 A GeV

A detailed study of chemical freeze-out in nucleus–nucleus collisions at beam energy 158 A GeV is presented. By analysing hadronic multiplicities within the statistical hadronization approach, the chemical equilibration of p–p, C–C, Si–Si and Pb–Pb systems is studied as a function of the number of participating nucleons in the system. Additionally, the two-component statistical hadronization model is applied to the data and is found to be able to explain the observed strangeness hadronic phase space under-saturation.

SHARE: Statistical hadronization with resonances

SHARE: Statistical hadronization with resonances

Multiplicities and bulk thermodynamic quantities at √SNN = 130 GeV with SHARE

We introduce the Statistical Hadronization with Resonances (SHARE) suite of programs and perform a study of particle multiplicities as well as bulk thermodynamic quantities for the RHIC Au–Au reactions at √SNN = 130 GeV. We also show that the statistical hadronization model, with parameters fitted to match pion, proton and hyperon ratios, in turn correctly and consistently reproduces rapidity particle multiplicity.

What is the meaning of the statistical hadronization model?

The statistical model of hadronization succeeds in reproducing particle abundances and transverse momentum spectra in high energy collisions of elementary particles as well as of heavy ions. Despite its apparent success, the interpretation of these results is controversial and the validity of the approach very often questioned. In this paper, we would like to summarize the whole issue by first outlining a basic formulation of the model and then comment on the main criticisms and different kinds of interpretations, with special emphasis on the so-called "phase space dominance". While the ultimate answer to the question why the statistical model works should certainly be pursued, we stress that it is a priority to confirm or disprove the fundamental scheme of the statistical model by performing some detailed tests on the rates of exclusive channels at lower energy.

Statistical hadronization and hadronic micro-canonical ensemble II

We present a Monte-Carlo calculation of the microcanonical ensemble of the of the ideal hadron-resonance gas including all known states up to a mass of about 1.8 GeV and full quantum statistics. The microcanonical average multiplicities of the various hadron species are found to converge to the canonical ones for moderately low values of the total energy, around 8 GeV, thus bearing out previous analyses of hadronic multiplicities in the canonical ensemble. The main numerical computing method is an importance sampling Monte-Carlo algorithm using the product of Poisson distributions to generate multi-hadronic channels. It is shown that the use of this multi-Poisson distribution allows an efficient and fast computation of averages, which can be further improved in the limit of very large clusters. We have also studied the fitness of a previously proposed computing method, based on the Metropolis Monte-Carlo algorithm, for event generation in the statistical hadronization model. We find that the use of the multi-Poisson distribution as proposal matrix dramatically improves the computation performance. However, due to the correlation of subsequent samples, this method proves to be generally less robust and effective than the importance sampling method.