arXiv subjects

Mark I. Gorenstein

Publications and source records attributed to Mark I. Gorenstein.

At least 37 records · Page 2Linked to original sources

arXiv2018

Non-congruent phase transitions in strongly interacting matter within the Quantum van der Waals model

The non-congruent liquid-gas phase transition (LGPT) in asymmetric nuclear matter is studied using the recently developed Quantum van der Waals model in the grand canonical ensemble. Different values of the electric-to-baryon charge ratio, $Q/B$, are considered. This non-congruent LGPT exhibits several features which are not present in the congruent LGPT of symmetric nuclear matter. These include a continuous phase transformation, a change in the location of the critical point, and the separation of the critical point and the endpoints. The effects which are associated with the non-congruent LGPT become negligible for the following cases: when $Q/B$ approaches its limiting values, $0.5$ or $0$, or if quantum statistical effects can be neglected. The latter situation is realized when the particle degeneracy attains large values, $g\gtrsim 10$.

hep-ph↗

arXiv2018

Monte Carlo approach to the excluded-volume hadron resonance gas in grand canonical and canonical ensembles

The Monte Carlo (MC) procedure for sampling the hadron yields within hadron resonance gas (HRG) model is presented. The effects of excluded-volume due to the finite hadron eigenvolumes and of exact charge conservation within the canonical ensemble (CE) formulation are simultaneously taken into account with the help of the importance sampling technique combined with the rejection sampling. The MC procedure allows one to calculate arbitrary moments of the event-by-event hadron yields. Note that the CE formulation for the excluded-volume HRG has not been considered before. The MC simulations coincide with the known analytic results in the thermodynamic limit for the excluded-volume HRG in the grand canonical ensemble and for the CE of non-interacting particles. The MC procedure is applied to study the simultaneous excluded-volume and CE effects. These effects are considered within the full HRG to calculate the particle number fluctuations and to estimate the finite size effects.

nucl-th↗

arXiv2018

Event-by-event fluctuations in p+p and central A+A collisions within relativistic transport models

Event-by-event multiplicity fluctuations in nucleus-nucleus collisions are studied within the relativistic transport models: EPOS, PHSD, and UrQMD. As measures of particle number fluctuations we consider the scaled variances $ω[X]$ for positive, negative, and all charged hadrons, and the strongly intensive quantities $Δ[K^+,π^+],$ $Σ[K^+,π^+]$ for $K^+$ and $π^+$ yields. At the SPS energy range the fluctuation measures are calculated for proton-proton, Ar+Sc, and Pb+Pb collisions. Comparison with recent NA61/SHINE and older NA49 measurements of the multiplicity fluctuations is done. A validity of the model of independent sources, a role of the experimental acceptance, and the centrality selection procedure are studied.Event-by-event multiplicity fluctuations in nucleus-nucleus collisions are studied within the relativistic transport models: EPOS, PHSD, and UrQMD. As measures of particle number fluctuations we consider the scaled variances $ω[X]$ for positive, negative, and all charged hadrons, and the strongly intensive quantities $Δ[K^+,π^+],$ $Σ[K^+,π^+]$ for $K^+$ and $π^+$ yields. At the SPS energy range the fluctuation measures are calculated for proton-proton, Ar+Sc, and Pb+Pb collisions. Comparison with recent NA61/SHINE and older NA49 measurements of the multiplicity fluctuations is done. A validity of the model of independent sources, a role of the experimental acceptance, and the centrality selection procedure are studied.

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arXiv2018

Finite resonance widths influence the thermal-model description of hadron yields

Different scenarios for modeling resonances in a thermal model description of hadron yields measured in heavy-ion collisions are explored: the zero-width approximation, the energy independent Breit-Wigner scheme, and the energy dependent Breit-Wigner (eBW) scheme. Application of the eBW scheme leads to a notable suppression in the proton yields, stemming mainly from a reduced feeddown from $Δ$ resonances because of the threshold effects. A significantly improved agreement of thermal model with hadron yields measured in Pb-Pb collisions at $\sqrt{s_{_{NN}}} = 2.76$ TeV by the ALICE collaboration is obtained in the eBW scheme at $T \simeq 155$ MeV, indicating a possible resolution of the so-called 'proton anomaly'. The results obtained show that there are significant systematic uncertainties in the thermal model due to the modeling of broad resonances.

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arXiv2018

Critical point of nuclear matter and beam energy dependence of net proton number fluctuations

The beam energy dependence of net baryon number susceptibilities is studied in the framework of the hadron resonance gas model with the attractive and repulsive van der Waals interactions between baryons. The collision energy dependences for the skewness $Sσ$ and kurtosis $κσ^2$ deviate significantly from the Poisson baseline and demonstrate the existence of rich structures at moderate collision energies. This behavior may result from the critical end point of the nuclear liquid-gas first order phase transition. In particular, $κσ^2$ shows a non-monotonic energy dependence, and, in contrast to the standard scenario for the QCD critical point, it does not decrease at low collision energies. It is also found that the measurable net proton fluctuations differ significantly from the net baryon fluctuations when interactions between baryons cannot be neglected. The results are compared with the experimental net proton number fluctuations measured by the STAR collaboration.

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arXiv2018

Beth-Uhlenbeck approach for repulsive interactions between baryons in a hadron gas

The quantum mechanical Beth-Uhlenbeck (BU) approach for repulsive hard-core interactions between baryons is applied to the thermodynamics of a hadron gas. The second virial coefficient $a_2$ -- the "excluded volume" parameter -- calculated within the BU approach is found to be temperature dependent, and it differs dramatically from the classical excluded volume (EV) model result. At temperatures $T =100-200$ MeV, the widely used classical EV model underestimates the EV parameter for nucleons at a given value of the nucleon hard-core radius by large factors of 3-4. Previous studies, which employed the hard-core radii of hadrons as an input into the classical EV model, have to be re-evaluated using the appropriately rescaled EV parameters. The BU approach is used to model the repulsive baryonic interactions in the hadron resonance gas (HRG) model. Lattice data for the second and fourth order net baryon susceptibilities are described fairly well when the temperature dependent BU baryonic excluded volume parameter corresponds to nucleon hard-core radii of $r_c = 0.25-0.3$ fm. Role of the attractive baryonic interactions is also considered. It is argued that HRG model with a constant baryon-baryon EV parameter $v_{NN} \simeq 1$ fm$^3$ provides a simple yet efficient description of baryon-baryon interaction in the crossover temperature region.

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arXiv2017

van der Waals Interactions and Hadron Resonance Gas: Role of resonance widths modeling on conserved charges fluctuations

The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons -- the QvdW-HRG model -- is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for $χ_{11}^{BQ} / χ_2^B$, effects of the QvdW interactions essentially cancel out. It is found that the inclusion of the finite resonance widths leads to an improved description of $χ_2^B$, but it also leads to a worse description of $χ_{11}^{BQ} / χ_2^B$, as compared to the lattice data. On the other hand, inclusion of the extra, unconfirmed baryons into the hadron list leads to a simultaneous improvement in the description of both observables.

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arXiv2017

Multicomponent van der Waals equation of state: Applications in nuclear and hadronic physics

A generalization of the quantum van der Waals equation of state for a multi-component system in the grand canonical ensemble is proposed. The model includes quantum statistical effects and allows to specify the parameters characterizing repulsive and attractive forces for each pair of particle species. The model can be straightforwardly applied to the description of asymmetric nuclear matter and also for mixtures of interacting nucleons and nuclei. Applications of the model to the equation of state of an interacting hadron resonance gas are discussed.

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arXiv2017

Modeling baryonic interactions with the Clausius-type equation of state

The quantum statistical Clausius-based equation of state is used to describe the system of interacting nucleons. The interaction parameters $a$, $b$, and $c$ of the model are fixed by the empirically known nuclear ground state properties and nuclear incompressibility modulus. The model is generalized to describe the baryon-baryon interactions in the hadron resonance gas (HRG). The predictions of such a Clausius-HRG model are confronted with the lattice QCD data at zero and at small chemical potentials, and are also contrasted with the standard van der Waals approach. It is found that the behavior of the lattice QCD observables in a high-temperature hadron gas is sensitive to the nuclear matter properties. An improved description of the nuclear incompressibility factor correlates with an improved description of the lattice QCD data in the crossover transition region.

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arXiv2017

van der Waals Interactions in Hadron Resonance Gas: From Nuclear Matter to Lattice QCD

An extension of the ideal hadron resonance gas (HRG) model is constructed which includes the attractive and repulsive van der Waals (VDW) interactions between baryons. This VDW-HRG model yields the nuclear liquid-gas transition at low temperatures and high baryon densities. The VDW parameters $a$ and $b$ are fixed by the ground state properties of nuclear matter, and the temperature dependence of various thermodynamic observables at zero chemical potential are calculated within VDW-HRG model. Compared to the ideal HRG model, the inclusion of VDW interactions between baryons leads to a qualitatively different behavior of second and higher moments of fluctuations of conserved charges, in particular in the so-called crossover region $T\sim 140 - 190$ MeV. For many observables this behavior resembles closely the results obtained from lattice QCD simulations. This hadronic model also predicts nontrivial behavior of net-baryon fluctuations in the region of phase diagram probed by heavy-ion collision experiments. These results imply that VDW interactions play a crucial role in thermodynamics of hadron gas. Thus, the commonly performed comparisons of the ideal HRG model with the lattice and heavy-ion data may lead to misconceptions and misleading conclusions.

hep-ph↗

arXiv2015

New Theoretical Results on Event-by-Event Fluctuations

Several theoretical results concerning event-by-event fluctuations are discussed: (1) a role of the global conservation laws and concept of statistical ensembles; (2) strongly intensive measures are introduced; they give a possibility to study e-by-e fluctuations for physical systems with volume fluctuations; (3) identity method for chemical fluctuations in a case of incomplete particle identification; (4) the example of particle number fluctuations in a vicinity of the critical point.

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arXiv2015

Strongly Intensive Measures for Particle Number Fluctuations: Effects of Hadronic Resonances

Strongly intensive measures $Δ$ and $Σ$ are used to study event-by-event fluctuations of hadron multiplicities in nucleus-nucleus collisions. The effects of resonance decays are investigated within statistical model and relativistic transport model. Two specific examples are considered: resonance decays to two positively charged particles (e.g., $Δ^{++}\rightarrow p+ π^+$) and to $π^+π^-$-pairs. (e.g., $ρ^0\rightarrow π^-+π^+$). It is shown that resonance abundances at the chemical freeze-out can be estimated by measuring the fluctuations of the number of stable hadrons. These model results are compared to the full hadron-resonance gas analysis within both the grand canonical and canonical ensemble. The ultra-relativistic quantum molecular dynamics (UrQMD) model of nucleus-nucleus collisions is used to illustrate the role of global charge conservation, centrality selection, and limited experimental acceptance.

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arXiv2015

Hagedorn's Hadron Mass Spectrum and the Onset of Deconfinement

A brief history of the observation of the onset of deconfinement - the beginning of the creation of quark gluon plasma in nucleus-nucleus collisions with increasing collision energy - is presented. It starts with the measurement of hadron mass spectrum and the Hagedorn's hypothesis of the limiting temperature of hadronic matter (the Hagedorn temperature). Then the conjecture that the Hagedorn temperature is the phase transition temperature was formulated with the crucial Hagedorn participation. It was confirmed by the observation of the onset of deconfinement in lead-lead collisions at the CERN SPS energies.

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arXiv2014

Strongly Intensive Measures for Transverse Momentum and Particle Number Fluctuations

The strongly intensive measures $Δ[P_T,N]$ and $Σ[P_T,N]$ are used to study the event-by-event fluctuations of the transverse momentum $P_T$ and particle multiplicity $N$ in nucleus-nucleus collisions. A special normalization for these fluctuation measures ensures that they are dimensionless and yields a common scale required for a quantitative comparison of fluctuations. In this paper basic properties of the $Δ[P_T, N]$ and $Σ[P_T, N]$ measures are tested within different phenomenological models using the Monte Carlo simulations (the so-called fast generators) and analytical solutions. The obtained results are helpful to elucidate the properties of $Δ[P_T,N]$ and $Σ[P_T,N]$ measures.

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arXiv2010

Equation of State for the Quark Gluon Plasma with the Negative Bag Constant

We propose a new analytical form of the quark-gluon plasma equation of state (EoS). This new EoS satisfies all qualitative features observed in the lattice QCD calculations and gives a good quantitative description of the lattice results in the SU(3) gluodynamics. The energy density for the suggested EoS looks similar to that in the bag model, but requires a negative value of the bag constant.

hep-ph↗

arXiv2009

Crossover to Cluster Plasma in the Gas of Quark-Gluon Bags

We study a smooth crossover transition in the gas of quark-gluon bags. The equation of state at high temperature is that of the quark-gluon plasma. However, the system consists of the bags with finite volumes which are defined by the model parameters of the mass-volume bag spectrum. Possible structures in this {\it cluster} quark-gluon plasma are classified.

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arXiv2008

Statistical Ensembles with Volume Fluctuations

The volume fluctuations in statistical mechanics are discussed. First, the volume fluctuations in ensembles with a fixed external pressure, the so called pressure ensembles, are considered. Second, a generalization of the pressure ensembles is suggested. Namely, the statistical ensembles with the volume fluctuating according to externally given distributions are considered. Several examples and possible applications in statistical models of hadron production are discussed.

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arXiv2003

Signals of Deconfinement Transition in Nucleus-Nucleus Collisions

We discuss the energy dependence of hadron production in relativistic nucleus-nucleus collisions. Several `anomalies' in the energy dependence have been predicted as signals of the deconfinement phase transition and three of these signals are observed at the CERN SPS indicating that the onset of deconfinement in Pb+Pb collisions is located at about 30 A GeV.

hep-ph↗