Volodymyr Vovchenko

Volodymyr Vovchenko
University of Washington Seattle | UW · Institute for Nuclear Theory

PhD

About

171
Publications
5,488
Reads
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1,991
Citations
Additional affiliations
April 2022 - present
University of Washington Seattle
Position
  • Professor (Assistant)
Description
  • Research Assistant Professor
February 2020 - March 2022
Lawrence Berkeley National Laboratory
Position
  • PostDoc Position
January 2017 - February 2020
Goethe-Universität Frankfurt am Main
Position
  • Wissenschaftlicher Mitarbeiter
Education
September 2007 - June 2013

Publications

Publications (171)
Preprint
I present an overview of recent theoretical results on fluctuations of conserved charges in heavy-ion collisions obtained in relativistic hydrodynamics and molecular dynamics frameworks. In particular, I discuss the constraints on the location of the QCD critical point based on comparisons of experimental data on proton number cumulants with precis...
Preprint
It is demonstrated that the presence of a phase transition in heavy ion collisions, at beam energies that probe dense QCD matter, leads to a significant enhancement of the dilepton yield per produced pion due to the extended emission time. In addition, the temperature of low mass dileptons shows a modest decrease due to the mixed phase. The emissio...
Preprint
Full-text available
In order to complete the Beam Energy Scan (BES) physics program, including the search for the QCD critical point, the extraction of the hyperon-nucleon interaction, and the determination of constraints on the nuclear matter equation of state at high baryon density, active US participation in the international collaboration of the Compressed Baryoni...
Preprint
This work incorporates the effect of short-range repulsion between particles into the Cooper-Frye hadron sampling procedure. This is achieved by means of a rejection sampling step, which prohibits any pair of particles from overlapping in the coordinate space, effectively modeling the effect of hard-core repulsion. The new procedure -- called the F...
Preprint
We analyze the behavior of (net-)proton number cumulants in central collisions of heavy ions across a broad collision energy range by utilizing hydrodynamic simulations. The calculations incorporate essential non-critical contributions to proton fluctuations such as repulsive baryonic core and exact baryon number conservation. The experimental data...
Article
We develop a framework to relate proton number cumulants measured in heavy-ion collisions within a momentum space acceptance to the susceptibilities of baryon number, assuming that particles are emitted from a fireball with uniform distribution of temperature and baryochemical potential, superimposed on a hydrodynamic flow velocity profile. The rap...
Article
Full-text available
We study fluctuations of particle number in the presence of a critical point by utilizing molecular dynamics simulations of the classical Lennard-Jones fluid in a periodic box. The numerical solution of the N-body problem naturally incorporates all correlations, exact conservation laws, and finite size effects, allowing us to study the fluctuation...
Preprint
We point out how proton number cumulants measured in heavy-ion collisions within a momentum space acceptance can be related to the grand-canonical cumulants of baryon number, assuming that particles are emitted from a fireball with uniform distribution of temperature and baryochemical potential, superimposed on a hydrodynamic flow velocity profile....
Article
We present results of a phase space coalescence approach within the UrQMD transport and -hybrid model for a very wide range of beam energies from SIS to LHC. The coalescence model is able to qualitatively describe the whole range of experimental data with a fixed set of parameters. Some systematic deviations are observed for very low beam energies...
Article
We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, κ2[B−B¯]/〈B+B¯〉, is sensitive to the possible modification of (anti)baryon yields due to BB¯ annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnitude of the BB¯ annihilation and its in...
Preprint
Full-text available
We study fluctuations of particle number in the presence of critical point by utilizing molecular dynamics simulations of the classical Lennard-Jones fluid in a periodic box. The numerical solution of the $N$-body problem naturally incorporates all correlations, exact conservation laws, and finite size effects, allowing us to study the fluctuation...
Article
The creation of loosely bound objects in heavy ion collisions, e.g. light clusters, near the phase transition temperature (Tch≈155 MeV) has been a puzzling observation that seems to be at odds with Big Bang nucleosynthesis suggesting that deuterons and other clusters are formed only below a temperature T≈0.1−1 MeV. We solve this puzzle by showing t...
Preprint
Full-text available
We investigate the chemical freeze-out in heavy-ion collisions (HICs) and the impact of the hadronic spectrum on thermal model analyses. Detailed knowledge of the hadronic spectrum is still an open question, which has phenomenological consequences on the study of HICs. By varying the number of resonances included in Hadron Resonance Gas (HRG) Model...
Article
Full-text available
We present a dynamical description of (anti)proton number cumulants and correlation functions in central Au-Au collisions at sNN=7.7–200GeV by utilizing viscous hydrodynamics simulations. The cumulants of proton and baryon number are calculated in a given momentum acceptance analytically, via an appropriately extended Cooper-Frye procedure describi...
Article
Full-text available
This paper introduces the subensemble acceptance method 2.0 (SAM-2.0)—a procedure to correct cumulants of a random number distribution inside a subsystem for the effect of exact global conservation of a conserved quantity to which this number is correlated, with applications to measurements of event-by-event fluctuations in heavy-ion collisions. Th...
Article
Full-text available
Utilizing viscous hydrodynamic simulations of heavy-ion collisions, we study the behavior of cumulants of (net-)(anti)proton number distributions at RHIC beam energy scan energies, incorporating non-critical contributions like baryon conservation and excluded volume. The experimental data on net-proton cumulants at √ S NN > 20 GeV are consistent wi...
Article
Full-text available
We investigate the chemical freeze-out in heavy-ion collisions (HICs) and the impact of the hadronic spectrum on thermal model analyses [1, 2]. Detailed knowledge of the hadronic spectrum is still an open question, which has phenomenological consequences on the study of HICs. By varying the number of resonances included in Hadron Resonance Gas (HRG...
Article
We simultaneously incorporate two common extensions of the hadron resonance gas model, namely the addition of extra, unconfirmed resonances to the particle list, and the excluded volume repulsive interactions. We emphasize the complementary nature of these two extensions and identify combinations of conserved charge susceptibilities that allow us t...
Preprint
A brief overview of the recent developments concerning theoretical description of event-by-event fluctuations in heavy-ion collisions is presented, with an emphasis on the role of exact conservation laws and calculations based on relativistic hydrodynamics.
Article
The thermal fit to preliminary HADES data of Au+Au collisions at sNN=2.4 GeV shows two degenerate solutions at T≈50 MeV and T≈70 MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number o...
Article
The Beam Energy Scan Theory (BEST) Collaboration was formed with the goal of providing a theoretical framework for analyzing data from the Beam Energy Scan (BES) program at the relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory. The physics goal of the BES program is the search for a conjectured QCD critical point as well as f...
Preprint
We present results of a phase space coalescence approach within the UrQMD transport and -hybrid model for a very wide range of beam energies from SIS to LHC. The coalescence model is able to qualitatively describe the whole range of experimental data with a fixed set of parameters. Some systematic deviations are observed for very low beam energies...
Preprint
Full-text available
The Beam Energy Scan Theory (BEST) Collaboration was formed with the goal of providing a theoretical framework for analyzing data from the Beam Energy Scan (BES) program at the relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory. The physics goal of the BES program is the search for a conjectured QCD critical point as well as f...
Preprint
We simultaneously incorporate two common extensions of the hadron resonance gas model, namely the addition of extra, unconfirmed resonances to the particle list and the excluded volume repulsive interactions. We emphasize the complementary nature of these two extensions and identify combinations of conserved charge susceptibilities that allow to co...
Preprint
We present a dynamical description of (anti)proton number fluctuations cumulants and correlation functions in central Au-Au collisions at $\sqrt{s_{\rm NN}} = 7.7-200$ GeV by utilizing viscous hydrodynamics simulations. The cumulants of proton and baryon number are calculated in a given momentum acceptance analytically, via an appropriately extende...
Preprint
We introduce the subensemble acceptance method 2.0 (SAM-2.0) -- a procedure to correct cumulants of a random number distribution inside a subsystem for the effect of exact global conservation of a conserved quantity to which this number is correlated, with applications to measurements of event-by-event fluctuations in heavy-ion collisions. The meth...
Preprint
Full-text available
We point out that the variance of net-baryon distribution normalized by the Skellam distribution baseline, $\kappa_2[B-\bar{B}]/\langle B+\bar{B}\rangle$, is sensitive to the possible modification of (anti)baryon yields due to $B\bar{B}$ annihilation in the hadronic phase. The corresponding measurements can thus place stringent limits on the magnit...
Article
Full-text available
Equation of state and electric (isospin) charge fluctuations are studied for matter composed of interacting pions. The pion matter is described by self interacting scalar fields via a ϕ4−ϕ6-type Lagrangian. The mean-field approximation is used, and interaction parameters are fixed by fitting lattice QCD results on the isospin density as a function...
Preprint
Full-text available
We study the applicability of a Deep Neural Network (DNN) approach to simulate one-dimensional non-relativistic fluid dynamics. Numerical fluid dynamical calculations are used to generate training data-sets corresponding to a broad range of profiles to perform supervised learning with DNN. The performance of the DNN approach is analyzed, with a foc...
Preprint
The thermal fit to preliminary HADES data of Au+Au collisions at $\sqrt{s_{_{NN}}}=2.4$ GeV shows two degenerate solutions at $T\approx50$ MeV and $T\approx70$ MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both so...
Article
Full-text available
We revisit the problem of particlization of a QCD fluid into hadrons and resonances at the end of the fluid dynamical stage in relativistic heavy-ion collisions in a context of fluctuation measurements. The existing methods sample an ideal hadron resonance gas, and therefore, they do not capture the non-Poissonian nature of the grand-canonical fluc...
Article
In this note we discuss subtleties associated with the efficiency corrections for measurements of off-diagonal cumulants and factorial moments for a situation when one deals with overlapping sets of particles, such as correlations between numbers of protons and positively charged particles. In particular, we discuss the situation commonly encounter...
Article
Full-text available
General formulas are presented for higher order cumulants of the conserved charge statistical fluctuations inside the mixed phase. As a particular example, the van der Waals model in the grand canonical ensemble is used. The higher order measures of the conserved charge fluctuations up to the hyperkurtosis are calculated in a vicinity of the critic...
Preprint
We report on recent progress concerning theoretical description of event-by-event fluctuations in heavy-ion collisions. Specifically we discuss a new Cooper-Frye particlization routine -- the subensemble sampler -- which is designed to incorporate effects of global conservation laws, thermal smearing and resonance decays on fluctuation measurements...
Preprint
Full-text available
Equation of state and electric (isospin) charge fluctuations are studied for matter composed of interacting pions. The pion matter is described by self interacting scalar fields via a $\phi^4-\phi^6$ type Lagrangian. The mean-field approximation is used, and interaction parameters are fixed by fitting lattice QCD results on the isospin density as a...
Article
Full-text available
We investigate the possible formation of a Bose-Einstein condensed phase of pions in the early Universe at nonvanishing values of lepton flavor asymmetries. A hadron resonance gas model with pion interactions, based on first-principle lattice QCD simulations at nonzero isospin density, is used to evaluate cosmic trajectories at various values of el...
Preprint
In this note we discuss subtleties associated with the efficiency corrections for measurements of off-diagonal cumulants and factorial moments for a situation when one deals with overlapping sets of particles, such as correlations between numbers of protons and positively charged particles. We present the efficiency correction formulas for the case...
Article
The thermodynamic properties of high temperature and high density QCD-matter are studied using the Chiral SU(3)-flavor parity-doublet Polyakov-loop quark-hadron mean-field model, CMF. The CMF model provides a proper description of lattice QCD data, heavy-ions physics, and static neutron stars. The behavior of lines of constant pressure with increas...
Article
We report on recent progress concerning effects of global conservation laws on cumulants of conserved quantities. Specifically, we will relate for an arbitrary equation of state cumulants of a conserved charge measured in a subvolume of a thermal system with the corresponding grandcanonical susceptibilities, taking into account exact global conserv...
Article
We report on recent progress concerning the theoretical description of event-by-event fluctuations in heavy-ion collisions. Specifically, we discuss a new Cooper–Frye particlization routine — the subensemble sampler — which is designed to incorporate effects of global conservation laws, thermal smearing and resonance decays on fluctuation measureme...
Preprint
We revisit the problem of particlization of a QCD fluid into hadrons and resonances at the end of the fluid dynamical stage in relativistic heavy-ion collisions in a context of fluctuation measurements. The existing methods sample an ideal hadron resonance gas, therefore, they do not capture the non-Poissonian nature of the grand-canonical fluctuat...
Article
Full-text available
We derive the relation between cumulants of a conserved charge measured in a subvolume of a thermal system and the corresponding grand-canonical susceptibilities, taking into account exact global conservation of that charge. The derivation is presented for an arbitrary equation of state, with the assumption that the subvolume is sufficiently large...
Preprint
General formulas are presented for higher order cumulants of the conserved charge statistical fluctuations inside the mixed phase. As a particular example the van der Waals model in the grand canonical ensemble is used. The higher order measures of the conserved charge fluctuations up to the hyperkurtosis are calculated in a vicinity of the critica...
Chapter
The QCD equation of state at finite temperature and densities of conserved charges is considered in the framework of a Hagedorn bag-like model, incorporating both the finite sizes of hadrons as well as their exponential mass spectrum. Augmented with non-zero masses of quarks and gluons in the bag spectrum, the model yields a fair quantitative descr...
Article
Full-text available
A bstract We analyze the behavior of cumulants of conserved charges in a subvolume of a thermal system with exact global conservation laws by extending a recently developed subensemble acceptance method (SAM) [1] to multiple conserved charges. Explicit expressions for all diagonal and off-diagonal cumulants up to sixth order that relate them to the...
Article
Full-text available
The role of repulsive interactions in statistical systems of Bose particles is investigated. Three different phenomenological frameworks are considered: a mean-field model, an excluded volume model, and a model with a medium-dependent effective mass. All three models are tuned to yield similar equations of state, with only minor deviations from the...
Preprint
Full-text available
We investigate the possible formation of a Bose-Einstein condensed phase of pions in the early Universe at nonvanishing values of lepton flavor asymmetries. A hadron resonance gas model with pion interactions, based on first-principle lattice QCD simulations at nonzero isospin density, is used to evaluate cosmic trajectories at various values of el...
Article
Full-text available
A method to determine the kinetic freeze-out temperature in heavy-ion collisions from measured yields of short-lived resonances is presented. The resonance production is treated in the framework of a thermal model with an evolution between chemical and kinetic freeze-outs. The yields of many short-lived resonances are suppressed at T=Tkin<Tch. We d...
Article
Full-text available
We investigate simultaneous effects of finite system size and global charge conservation on thermal fluctuations in the vicinity of a critical point. For that we consider a finite interacting system, which exchanges particles with a finite reservoir (thermostat), comprising a statistical ensemble that is distinct from the common canonical and grand...
Article
Full-text available
This report summarizes the presentations and discussions during the Rapid Reaction Task Force “Dynamics of critical fluctuations: Theory – phenomenology – heavy-ion collisions”, which was organized by the ExtreMe Matter Institute EMMI and held at GSI, Darmstadt, Germany in April 2019. We address the current understanding of the dynamics of critical...
Article
Full-text available
We estimate the feeddown contributions from decays of unstable A=4 and A=5 nuclei to the final yields of protons, deuterons, tritons, ³He, and ⁴He produced in relativistic heavy-ion collisions at sNN>2.4 GeV, using the statistical model. The feeddown contribution effects do not exceed 5% at LHC and top RHIC energies due to the large penalty factors...
Preprint
We analyze the behavior of cumulants of conserved charges in a subvolume of a thermal system with exact global conservation laws by extending a recently developed subensemble acceptance method (SAM) [V. Vovchenko et al., arXiv:2003.13905] to multiple conserved charges. Explicit expressions for all diagonal and off-diagonal cumulants up to sixth ord...
Article
Full-text available
Exciting new scientific opportunities are presented for the PANDA detector at the High Energy Storage Ring in the redefined \(\overline{\text {p}} \text {p}(A)\) collider mode, HESR-C, at the Facility for Antiproton and Ion Research (FAIR) in Europe. The high luminosity, \(L \sim 10^{31}\) cm\(^{-2}\) s\(^{-1}\), and a wide range of intermediate an...
Article
An overview of a hadron resonance gas (HRG) model that includes van der Waals (vdW) interactions between hadrons is presented. Applications of the excluded volume HRG model to heavy-ion collision data and lattice quantum chromodynamics (QCD) equation of state are discussed. A recently developed quantum vdW HRG model is covered as well. Applications...
Preprint
We investigate simultaneous effects of finite system size and global charge conservation on thermal fluctuations in the vicinity of a critical point. For that we consider a finite interacting system which exchanges particles with a finite reservoir (thermostat), comprising a statistical ensemble that is distinct from the common canonical and grand...
Preprint
The role of repulsive interactions in statistical systems of Bose particles is investigated. Three different phenomenological frameworks are considered: a mean field model, an excluded volume model, and a model with a medium dependent effective mass. All three models are tuned to yield similar equations of state, with only minor deviations from the...
Preprint
An overview of a hadron resonance gas (HRG) model that includes van der Waals interactions between hadrons is presented. Applications of the excluded volume HRG model to heavy-ion collision data and lattice QCD equation of state are discussed. A recently developed quantum van der Waals hadron resonance gas model is covered as well. Applications of...
Preprint
We estimate the feeddown contributions from decays of unstable $A = 4$ and $A = 5$ nuclei to the final yields of protons, deuterons, tritons, $^3$He, and $^4$He produced in relativistic heavy-ion collisions at $\sqrt{s_{\rm NN}} > 2.4$ GeV, using the statistical model. The feeddown contribution effects do not exceed 5% at LHC and top RHIC energies...
Preprint
We derive the relation between cumulants of a conserved charge measured in a subvolume of a thermal system and the corresponding grand-canonical susceptibilities, taking into account exact global conservation of that charge. The derivation is presented for an arbitrary equation of state, with the assumption that the subvolume is sufficiently large...
Chapter
Exciting new scientific opportunities are presented for the PANDA detector at the High Energy Storage Ring in the redefined \(\bar{\text {p}} \text {p}(A)\) collider mode, HESR-C, at the Facility for Antiproton and Ion Research (FAIR) in Europe. The high luminosity, \(L \sim 10^{31}\) cm\(^{-2}\) s\(^{-1}\), and a wide range of intermediate and hig...
Article
Full-text available
The nuclear liquid-gas transition at normal nuclear densities, n≈n0=0.16fm−3, and small temperatures, T≈20MeV, has a large influence on analytic properties of the QCD grand-canonical thermodynamic potential. A classical van der Waals equation is used to determine qualitatively these unexpected features due to dense cold matter. The existence of the...
Article
Full-text available
The thermodynamic properties of high temperature and high density QCD matter are explored within the chiral SU(3)-flavor parity-doublet Polyakov-loop quark-hadron mean-field model, CMF. The quark sector of the CMF model is tuned to describe the μB=0 thermodynamics data of lattice QCD. The resulting lines of constant physical variables as well as th...
Article
Full-text available
The binomial acceptance correction procedure is studied for particle number distributions detected in high-energy reactions in finite regions of the momentum space. We present acceptance correction formulas for scaled variance, skewness, and kurtosis. Our considerations include various specific types of particles—positively or negatively charged ba...
Preprint
The thermodynamic properties of high temperature and high density QCD-matter are studied using the Chiral SU(3)-flavor parity-doublet Polyakov-loop quark-hadron mean-field model, CMF. The CMF model provides a proper description of lattice QCD data, heavy-ions physics, and static neutron stars. The behavior of lines of constant pressure with increas...
Preprint
Full-text available
This report summarizes the presentations and discussions during the Rapid Reaction Task Force "Dynamics of critical fluctuations: Theory -- phenomenology -- heavy-ion collisions", which was organized by the ExtreMe Matter Institute EMMI and held at GSI, Darmstadt, Germany in April 2019. We address the current understanding of the dynamics of critic...
Article
Full-text available
The QCD baryon number density can formally be expanded into a Laurent series in fugacity, which is a relativistic generalization of Mayer’s cluster expansion. We determine properties of the cluster expansion in a model with a phase transition and a critical point at finite baryon density, in which the Fourier coefficients of the expansion can be de...
Article
Full-text available
Thermodynamic properties of systems with repulsive interactions are considered in the grand-canonical ensemble. The analytic structure of the excluded-volume model in the complex plane of the system chemical potential (fugacity) is elaborated, based on the fact that the pressure function can be given in terms of the Lambert W function. Even though...
Article
Full-text available
The system-size dependence of hadrochemistry at vanishing baryon density is considered within the canonical statistical model (CSM) with local exact conservation of three conserved charges, allowing for a possibility of strangeness undersaturation, i.e., γS≤1. Exact baryon number conservation is found to be even more important than that of strangen...
Preprint
The QCD equation of state at finite temperature and densities of conserved charges is considered in the framework of a Hagedorn bag-like model, incorporating both the finite sizes of hadrons as well as their exponential mass spectrum. Augmented with non-zero masses of quarks and gluons in the bag spectrum, the model yields a fair quantitative descr...
Article
Full-text available
The chemical freeze-out parameters in central nucleus-nucleus collisions are extracted consistently from hadron-yield data within the quantum van der Waals (QvdW) hadron resonance gas model. The beam energy dependencies for skewness and kurtosis of net baryon, net electric, and net strangeness charges are predicted. The QvdW interactions in asymmet...