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Exploring non-equilibrium quark-gluon plasma effects on charm transport coefficients
Nuclear Theory · Submitted 22 Oct 2019
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Thus each non-equilibrium scenario affects $A$ and $\hat{q}$ of charm quarks in a different way.
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The abstract, sentence by sentence
In this article we investigate how the drag coefficient $A$ and $\hat{q}$, the transverse momentum transfer by unit length, of charm quarks are modified if the QGP is not in complete thermal equilibrium using the dynamical quasi-particle model (DQPM) which reproduces both, the equation-of-state of the QGP and the spatial diffusion coefficient of heavy quarks as predicted by lattice QCD calculations. We study three cases: a) the QGP has an anisotropic momentum distribution of the partons which leads to an anisotropic pressure b) the QGP partons have higher or lower kinetic energies as compared to the thermal expectation value, and c) the QGP partons have larger or smaller pole masses of their spectral function as compared to the pole mass from the DQPM at the QGP temperature. In the last two cases we adjust the number density of partons to obtain the same energy density as in an equilibrated QGP. In the first scenario we find that if the transverse pressure exceeds the longitudinal one for small heavy quark momenta $A$ becomes larger and $\hat{q}$ smaller as compared to an isotropic pressure. For heavy quarks with large momentum both, $A$ and $\hat{q}$ , approach unity. If the partons have less kinetic energy or a smaller pole mass as compared to a system in equilibrium charm quarks lose more energy. In the former case $\hat{q}$ decreases whereas in the latter case it increases for charm quark with a low or intermediate transverse momentum. Thus each non-equilibrium scenario affects $A$ and $\hat{q}$ of charm quarks in a different way. The modifications in our scenarios are of the order 20-50\% at temperatures relevant for heavy ion reactions. These modifications have to be considered if one wants to determine these coefficients by comparing heavy ion data with theoretical predictions from viscous hydrodynamics or Langevin equations.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | In this article we investigate how the drag coefficient $A$ and $\hat{q}$, the transverse momentum transfer by unit length, of charm quarks are modified if the QGP is not in complete thermal equilibrium using the dynamical quasi-particle model (DQPM) which reproduces both, the equation-of-state of the QGP and the spatial diffusion coefficient of heavy quarks as predicted by lattice QCD calculations. | contribution 0.99 | 0.81 | 0.06 | asserted 0.79 |
| s1 | We study three cases: a) the QGP has an anisotropic momentum distribution of the partons which leads to an anisotropic pressure b) the QGP partons have higher or lower kinetic energies as compared to the thermal expectation value, and c) the QGP partons have larger or smaller pole masses of their spectral function as compared to the pole mass from the DQPM at the QGP temperature. | contribution 0.65 | 0.81 | 0.03 | asserted 0.96 |
| s2 | In the last two cases we adjust the number density of partons to obtain the same energy density as in an equilibrated QGP. | method 0.98 | 0.80 | 0.02 | asserted 0.98 |
| s3 | In the first scenario we find that if the transverse pressure exceeds the longitudinal one for small heavy quark momenta $A$ becomes larger and $\hat{q}$ smaller as compared to an isotropic pressure. | result 1.00 | 0.95 | 0.11 | asserted 1.00 |
| s4 | For heavy quarks with large momentum both, $A$ and $\hat{q}$ , approach unity. | result 1.00 | 0.87 | 0.06 | asserted 1.00 |
| s5 | If the partons have less kinetic energy or a smaller pole mass as compared to a system in equilibrium charm quarks lose more energy. | result 1.00 | 0.88 | 0.11 | asserted 1.00 |
| s6 | In the former case $\hat{q}$ decreases whereas in the latter case it increases for charm quark with a low or intermediate transverse momentum. | result 1.00 | 0.89 | 0.07 | asserted 1.00 |
| s7 | Thus each non-equilibrium scenario affects $A$ and $\hat{q}$ of charm quarks in a different way. | interpretation 0.54 | 0.85 | 0.51 | asserted 1.00 |
| s8 | The modifications in our scenarios are of the order 20-50\% at temperatures relevant for heavy ion reactions. | result 0.99 | 0.92 | 0.19 | asserted 1.00 |
| s9 | These modifications have to be considered if one wants to determine these coefficients by comparing heavy ion data with theoretical predictions from viscous hydrodynamics or Langevin equations. | interpretation 0.96 | 0.15 | 0.25 | asserted 0.89 |
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Original abstract
In this article we investigate how the drag coefficient $A$ and $\hat{q}$, the transverse momentum transfer by unit length, of charm quarks are modified if the QGP is not in complete thermal equilibrium using the dynamical quasi-particle model (DQPM) which reproduces both, the equation-of-state of the QGP and the spatial diffusion coefficient of heavy quarks as predicted by lattice QCD calculations. We study three cases: a) the QGP has an anisotropic momentum distribution of the partons which leads to an anisotropic pressure b) the QGP partons have higher or lower kinetic energies as compared to the thermal expectation value, and c) the QGP partons have larger or smaller pole masses of their spectral function as compared to the pole mass from the DQPM at the QGP temperature. In the last two cases we adjust the number density of partons to obtain the same energy density as in an equilibrated QGP. In the first scenario we find that if the transverse pressure exceeds the longitudinal one for small heavy quark momenta $A$ becomes larger and $\hat{q}$ smaller as compared to an isotropic pressure. For heavy quarks with large momentum both, $A$ and $\hat{q}$ , approach unity. If the partons have less kinetic energy or a smaller pole mass as compared to a system in equilibrium charm quarks lose more energy. In the former case $\hat{q}$ decreases whereas in the latter case it increases for charm quark with a low or intermediate transverse momentum. Thus each non-equilibrium scenario affects $A$ and $\hat{q}$ of charm quarks in a different way. The modifications in our scenarios are of the order 20-50\% at temperatures relevant for heavy ion reactions. These modifications have to be considered if one wants to determine these coefficients by comparing heavy ion data with theoretical predictions from viscous hydrodynamics or Langevin equations.
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References
How the literature uses it
20 arXiv papers cite this in 23 sentences
Papers citing it · 14 sentences without a confident label
Cites it as support 1 paper
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Effects of the pre-equilibrium phase are usually entirely ignored, but calculations recently performed in a framework of kinetic theory [ref] suggest that these effects are sizable.
Heavy Quarks Embedded in Glasma · Introduction · 0.97
Cites it as background 8 papers
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Recently, some works have been done to analyse the effects of shear and bulk viscous coefficients on heavy quark transport in the expanding medium [ref] .
Heavy quark transport in an anisotropic hot QCD medium: Collisional and Radiative processes · Introduction · 0.81
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Earlier, the anisotropic aspects have been studied in the context of electromagnetic probes [ref] , gluon self-energy [ref] , heavy quark and jet in the pre-equilibrium phase [ref] , to evaluate the impact of shear and bulk viscous coefficients of the HQs transport in the medium [ref] .
Heavy quark radiation in an anisotropic hot QCD medium · Introduction · 0.93
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We note that the transport coefficients for the charm quark have been studied within the DQPM in Refs. [ref] , and the scattering rate $Γ$ has been calculated in Ref. [ref] .
Exploring jet transport coefficients by elastic scattering in the strongly interacting quark-gluon plasma · On-shell case · 0.87
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