Extraction of heavy-flavor transport coefficients in QCD matter

Rapp, Ralf; Gossiaux, Pol Bernard; Andronic, A.; Averbeck, R.; Masciocchi, S.; Beraudo, A.; Bratkovskaya, Elena; Braun‐Munzinger, P.; Cao, Shanshan; Dainese, A.; Das, Santosh K.; Djordjevic, Magdalena; Greco, V.; He, Min; Hees, Hendrik van; Inghirami, Gabriele; Kaczmarek, Olaf; Lee, Y. J.; Liao, Jinfeng; Liu, S. Y. F.; Moore, Guy D.; Nahrgang, Marlene; Pawlowski, Jan M.; Petreczky, Péter; Plumari, Salvatore; Prino, F.; Shi, Shuzhe; Song, Taesoo; Stachel, J.; Vitev, Ivan; Wang, X. N.

doi:10.1016/j.nuclphysa.2018.09.002

Cited by 188 publications

(83 citation statements)

References 206 publications

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“…At low energy, the dominant contribution to the energy loss comes from the collision processes. The inmedium energy loss of HQ is manifested in the large elliptic flow i.e., v 2 and in the suppression of high momentum heavy flavored (HF) hadrons as compared to proton-proton collision [1][2][3][4][5][6][7].Heavy quarks are produced in the initial stages of the collisions during the hard scatterings governed by perturbative quantum chromodynamics (pQCD) mostly through gluon fusion [8]; for next-to-leading order production see Ref. [9,10].…”

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confidence: 99%

Heavy quark transport in a viscous semi-QGP

Singh

Mishra

2020

Phys. Rev. D

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We study the effect of shear and bulk viscosities on the heavy quark transport coefficient within the matrix model of semi QGP. Dissipative effects are incorporated through the first-order viscous correction in the quark/antiquark and gluon distribution function. It is observed that while the shear viscosity effects reduces the drag of heavy quark the bulk viscosity effects increase the drag and the diffusion coefficients of heavy quark. For finite values of η/s and ξ/s, Polyakov loop further decreases the drag and the diffusion coefficients as compared to perturbative QCD. I. INTRODUCTIONThe aim of heavy ion collision (HIC) experiments is to characterize the properties of the deconfined state of matter namely the quark-gluon plasma (QGP) which is being created in these collisions. In this regard, the energy loss of heavy quark (HQ); especially charm and bottom; in the QGP medium is considered as one of the promising probes of QGP. There are two mechanisms that contribute to the energy loss of HQ; one is the radiative energy loss (medium induced gluon radiation) and the other is the collisional energy loss (i.e., scattering of HQ with thermalized medium partons). At low energy, the dominant contribution to the energy loss comes from the collision processes. The inmedium energy loss of HQ is manifested in the large elliptic flow i.e., v 2 and in the suppression of high momentum heavy flavored (HF) hadrons as compared to proton-proton collision [1][2][3][4][5][6][7].Heavy quarks are produced in the initial stages of the collisions during the hard scatterings governed by perturbative quantum chromodynamics (pQCD) mostly through gluon fusion [8]; for next-to-leading order production see Ref. [9,10]. Because of the large mass of HQ as compared to the temperature ranges accessible in the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) energies, the thermal production of HQ is negligible. Hence, once produced in the hard collisions, HQ propagates throughout the space-time evolution of the medium and interact with the light thermal partons (light quarks and gluons). Thus, the resulting effect of the interaction of HQ with the bulk medium modifies the spectra of HF hadrons. The interaction of HQ with the bulk medium is described by the scattering of HQ with the light thermal partons of the medium. At low momentum, the dominant contribution to the HQ scattering off of light quark and gluon in the thermal medium comes from the elastic scatterings and can be described by the diffusion process akin to Brownian motion. In addition, the thermalization of HQ in the bulk medium is also slowed down due to its large mass. Hence, the transport of non-equilibrated HQ in the thermalized medium of light quark and gluons yield valuable information about the medium throughout its propagation. In particular, while the low momentum interaction of HQ with the bulk medium is characterized by the spatial diffusion coefficient, the energy loss of HQ is described by the drag coefficient.The electron-positron yield ass...

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confidence: 99%

Heavy quark transport in a viscous semi-QGP

Singh

Mishra

2020

Phys. Rev. D

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“…We see that in all three cases the modification of R AA is not negligible and p T dependent. Models, in which all three ingredients are rather different, may nevertheless give very similar R AA values, as has been observed in the past [58][59][60][61][62]. Therefore, the observables at hand will not allow to unambiguously determine these ingredients separately.…”

Section: Discussionmentioning

confidence: 91%

Traces of nonequilibrium effects, initial condition, bulk dynamics, and elementary collisions in the charm observables

Song

Moreau

et al. 2020

Phys. Rev. C

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Heavy quarks produced in relativistic heavy-ion collisions are known to be sensitive probes of the hot and dense QCD matter they traverse. In this manuscript we study how their dynamics is affected by the nature of the bulk evolution of the QCD matter, the initial condition of the system, and the treatment of elementary interactions between heavy quarks and the surrounding medium. For the same initial condition and the same QGP expansion scenario we discuss the consequences of the assumption of a local equilibrium by comparing the consequences for the nuclear modification factor RAA and the elliptic flows of charm quarks, scrutinizing the different components of the final distribution of charm quarks. For this purpose we employ the parton-hadron-string dynamics (PHSD) model, which is an off-shell microscopic transport approach, as well as the linearized-Boltzmann (LB) scheme obtained by coarse graining the PHSD bulk and assuming local equilibrium for the interactions of the charm quarks with the bulk. The RAA of charm quarks stemming from the later LB approach is also compared to a genuine fluid dynamics evolution initiated by the coarse grained PHSD, which allows to further assess the consequences of reducing the full n-body dynamics. We then proceed to a systematic comparison of PHSD (in its LB approximation) with MC@HQ, another transport model for heavy flavors which also relies on LB approach. In particular, we investigate the consequences for the nuclear modification factor of charm quarks if we vary separately the initial heavy quark distribution function in matter, the expansion dynamics of the QGP and the elementary interactions of heavy quarks of these models. We find that the results for both models vary significantly depending on the details of the calculation. However, both models achieve very similar predictions for key heavy quark observables for certain combinations of initial condition, bulk evolution and interactions. We conclude that this ambiguity limits our ability to determine the different properties of the system based on the current set of observables.

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“…This reduces the Boltzmann equation to a Langevin equation in which the time evolution of the heavy quark momentum is described by drag and dif- fusion coefficients in Eqs. (9)- (12). Usually these transport coefficients are calculated under the assumption that the expanding matter is always in thermal equilibrium.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore hydrodynamics is not applicable to heavy flavor particles, though it has been very successful for describing the dynamics of bulk particles. Usually a Langevin or a Boltzmann transport approach is used to describe the time evolution of heavy flavor particles in heavy-ion collisions [4][5][6][7][8][9][10][11][12][13]. The key ingredients of the Langevin approach as well as for viscous hydro calculations are transport coefficients which can be calculated from the scattering amplitudes of heavy flavor particle with light particles from the QGP [4,14].…”

Section: Introductionmentioning

confidence: 99%

Exploring non-equilibrium quark-gluon plasma effects on charm transport coefficients

et al. 2020

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Heavy flavor particles are promising probes for the properties of the quark-gluon plasma (QGP) which is produced in relativistic heavy-ion collisions. The interaction of heavy quarks with equilibrated matter can be described by transport coefficients. In heavy-ion collisions matter is not completely thermalized. In this article we investigate how the drag coefficient A andq , 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 quantum chromodynamics (lQCD) 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 andq smaller as compared to an isotropic pressure. For heavy quarks with large momentum both, A andq , 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 caseq 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 andq 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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Extraction of heavy-flavor transport coefficients in QCD matter

Cited by 188 publications

References 206 publications

Heavy quark transport in a viscous semi-QGP

Heavy quark transport in a viscous semi-QGP

Traces of nonequilibrium effects, initial condition, bulk dynamics, and elementary collisions in the charm observables

Exploring non-equilibrium quark-gluon plasma effects on charm transport coefficients

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