Improved single-particle phase-space distributions for viscous fluid dynamic models of relativistic heavy ion collisions

Damodaran, Mridula; Molnár, Denés; Barnaföldi, G. G.; Berényi, D.; Nagy-Egri, Máté Ferenc

doi:10.1103/physrevc.102.014907

Cited by 7 publications

(9 citation statements)

References 24 publications

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“…All these chemical potentials are zero in this work, µ B = µ S = µ Q = 0, reflecting the approximately zero net baryon, strangeness and electric charge near midrapidity at top RHIC and LHC collision energies. As it is, the QGP is a dissipative fluid with nonzero dissipative flows contributing to T µν on the particlization surface, and since hydrodynamics does not provide any microscopic information on how the system evolved to this surface we are left with a large and irreducible ambiguity as to the choice of local momentum distributions for the different hadron species [95][96][97][98].…”

Section: Particlizationmentioning

confidence: 99%

Multisystem Bayesian constraints on the transport coefficients of QCD matter

Everett¹,

Ke²,

Paquet³

et al. 2021

Phys. Rev. C

204

158

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We study the properties of the strongly-coupled quark-gluon plasma with a multistage model of heavy ion collisions that combines the TRENTo initial condition ansatz, free-streaming, viscous relativistic hydrodynamics, and a relativistic hadronic transport. A model-to-data comparison with Bayesian inference is performed, revisiting assumptions made in previous studies. The role of parameter priors is studied in light of their importance towards the interpretation of results. We emphasize the use of closure tests to perform extensive validation of the analysis workflow before comparison with observations. Our study combines measurements from the Large Hadron Collider and the Relativistic Heavy Ion Collider, achieving a good simultaneous description of a wide range of hadronic observables from both colliders. The selected experimental data provide reasonable constraints on the shear and the bulk viscosities of the quark-gluon plasma at T ∼ 150-250 MeV, but their constraining power degrades at higher temperatures T 250 MeV. Furthermore, these viscosity constraints are found to depend significantly on how viscous corrections are handled in the transition from hydrodynamics to the hadronic transport. Several other model parameters, including the free-streaming time, show similar model sensitivity, while the initial condition parameters associated with the TRENTo ansatz are quite robust against variations of the particlization prescription. We also report on the sensitivity of individual observables to the various model parameters. Finally, Bayesian model selection is used to quantitatively compare the agreement with measurements for different sets of model assumptions, including different particlization models and different choices for which parameters are allowed to vary between RHIC and LHC energies. CONTENTS Pratt-Torrieri-Bernhard 10 D. Hadronic transport 11 IV. Specifying prior knowledge 11 V. Bayesian Parameter Estimation with a Statistical Emulator 13 A. Overview of Bayesian Parameter Estimation 13 B. Physical model emulator 14 C. Treatment of uncertainties 16 D. Sampling of the posterior 17 E. Maximizing the posterior 17 VI. Closure Tests 17 A. Validating Bayesian inference with closure tests 18 B. Guiding analyses with closure tests 18 37 A. Full posterior of model parameters 37 B. Posterior for LHC and RHIC independently 37 C. Validation of principal component analysis 37 D. Experimental covariance matrix 38 E. Reducing experimental uncertainty 39 F. Bulk relaxation time 39 G. Comparison to previous studies 40 1. Physics models 41 2. Prior distributions 42 3. Experimental data 42 H. Multistage model validation 42 1. Validation of second-order viscous hydrodynamics implementation 42 a. Validation against cylindrically symmetric external solution 43 2. SMASH 43 3. Comparison of JETSCAPE with hic-eventgen 45 4. The σ meson 46 5. Sampling particles on mass-shell 47 6. QCD equations of state with different hadron resonance gases 47 References 48

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Section: Particlizationmentioning

confidence: 99%

Multisystem Bayesian constraints on the transport coefficients of QCD matter

Everett¹,

Ke²,

Paquet³

et al. 2021

Phys. Rev. C

204

158

View full text Add to dashboard Cite

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“…In kinetic theory, it implies that their momentum distribution is given by the Bose-Einstein or Fermi-Dirac distribution. In the more general case where there is dissipation in hydrodynamics, there is an off-equilibrium correction to the hadron distribution, and this viscous correction is model dependent [30][31][32]. In this work, we use the "Grad" model [33] for viscous corrections to the equilibrium distribution function, the one out of several studied in Refs.…”

Section: A Multistage Model Of Heavy Ion Collisionsmentioning

confidence: 99%

Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions

Everett¹,

Oliinychenko²,

Luzum³

et al. 2022

Preprint

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We use a Bayesian-calibrated multistage viscous hydrodynamic model to explore deuteron yield, mean transverse momentum and flow observables in LHC Pb-Pb collisions. We explore theoretical uncertainty in the production of deuterons, including (i) the contribution of thermal deuterons, (ii) models for the subsequent formation of deuterons (hadronic transport vs coalescence) and (iii) the overall sensitivity of the results to the hydrodynamic model -in particular to bulk viscosity, which is often neglected in studies of deuteron production. Using physical parameters set by a comparison to only light hadron observables, we find good agreement with measurements of the mean transverse momentum pT and elliptic flow v2 of deuterons; however, tension is observed with experimental data for the deuteron multiplicity in central collisions. The results are found to be sensitive to each of the mentioned theoretical uncertainties, with a particular sensitivity to bulk viscosity, indicating that the latter is an important ingredient for an accurate treatment of deuteron production. I. INTRODUCTIONUltra-relativistic ion collisions produce a hot stronglycoupled plasma of quarks and gluons which expands, cools down and recombines into pions, nucleons, other

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“…However, our model of the QGP fluid is dissipative. Since hydrodynamics does not provide any microscopic information on how the system evolved to this surface, we are left with a large and irreducible ambiguity as to the choice of local momentum distributions and chemical abundances of the different hadron species [97][98][99][100]. The macroscopic dissipative currents π µν and Π reflect deviations of the hadrons' microscopic momentum distributions and yields from local thermodynamic equilibrium.…”

Section: Converting Fluids To Particlesmentioning

confidence: 99%

“…The capability of any of these models to describe correctly the momenta and chemistry of a realistic out-of-equilibrium system of hadrons is still under investigation (see Ref. [99,100] and references therein for a recent overview). For instance, all of these particlization models assume that the hydrodynamic shear stress is shared "democratically" among the hadronic species.…”

Section: Mapping Hydrodynamic Fields To Hadronic Momentum Distributionsmentioning

confidence: 99%

“…Refs. [97][98][99][100]159]) may be able to shed more light on this question and provide additional insights that exclude certain particlization models or build more realistic ones. Until this happens the particlization model uncertainty must be considered as "irreducible" and can be propagated for by Bayesian Model Averaging as reported in Ch.…”

Section: Mapping Hydrodynamic Fields To Hadronic Momentum Distributionsmentioning

confidence: 99%

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Quantifying the Quark Gluon Plasma

Everett¹

2021

Preprint

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The study of heavy-ion collisions presents a challenge to both theoretical and experimental nuclear physics. Due to the extremely short (10 −23 s) lifetime and small size (10 −14 m) of the collision system, disentangling information provided by experimental observables and progress in physical insight requires the careful application of plausible reasoning.I apply a program of statistical methodologies, primarily Bayesian, to quantify properties of the medium in specific models, as well as compare and criticize differing models of the system. Of particular interest are estimations of the specific shear and bulk viscosities, where we find that information carried by the experimental data is still limited. In particular we find a large sensitivity to prior assumptions at high temperatures. Moreover, sensitivities to model assumptions are present at low temperatures, and this source of model uncertainty is propagated with model averaging and model mixing.

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Improved single-particle phase-space distributions for viscous fluid dynamic models of relativistic heavy ion collisions

Cited by 7 publications

References 24 publications

Multisystem Bayesian constraints on the transport coefficients of QCD matter

Multisystem Bayesian constraints on the transport coefficients of QCD matter

Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions

Quantifying the Quark Gluon Plasma

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