Impact of momentum space anisotropy on heavy quark dynamics in a QGP medium (original) (raw)
Related papers
Heavy quark transport in an anisotropic hot QCD medium: Collisional and radiative processes
Physical Review D, 2021
The impact of momentum anisotropy on the heavy quark transport coefficients due to collisional and radiative processes in the QCD medium has been studied within the ambit of kinetic theory. Anisotropic aspects (momentum) are incorporated into the heavy quark dynamics through the non-equilibrium momentum distribution function of quarks, antiquarks, and gluons. These non-equilibrium distribution functions that encode the physics of momentum anisotropy and turbulent chromo-fields have been obtained by solving the ensemble-averaged diffusive Vlasov-Boltzmann equation. The momentum dependence of heavy quark transport coefficients in the medium is seen to be sensitive to the strength of the anisotropy for both collisional and radiative processes. In addition, the collisional and radiative energy loss of the heavy quark in the anisotropic hot QCD medium have been analyzed. The effects of anisotropy on the drag and diffusion coefficients are observed to have a visible impact on the nuclear suppression factor both at the RHIC and LHC.
Drag and diffusion of heavy quarks in a hot and anisotropic QCD medium
The European Physical Journal A
The propagation of heavy quarks (HQs) in a medium was quite often modeled by the Fokker-Plank (FP) equation. Since the transport coefficients, related to drag and diffusion processes are the main ingredients in the FP equation, the evolution of HQs is thus effectively controlled by them. At the initial stage of the relativistic heavy ion collisions, asymptotic weak-coupling causes the free-streaming motions of partons in the beam direction and the expansion in transverse directions are almost frozen, hence an anisotropy in the momentum space sets in. Since HQs are too produced in the same time therefore the study of the effect of momentum anisotropy on the drag and diffusion coefficients becomes advertently desirable. In this article we have thus studied the drag and diffusion of HQs in the anisotropic medium and found that the presence of the anisotropy reduces both drag and diffusion coefficients. In addition, the anisotropy introduces an angular dependence to both the drag and diffusion coefficients, as a result both coefficients get inflated when the partons are moving transverse to the direction of anisotropy than parallel to the direction of anisotropy.
Heavy-quark transport coefficients in a hot viscous quark–gluon plasma medium
Journal of Physics G: Nuclear and Particle Physics, 2013
The heavy-quark (HQ) transport coefficients have been estimated for a viscous quark-gluon plasma medium, utilizing a recently proposed quasi-particle description based on a realistic QGP equation of state (EoS). Interactions entering through the equation of state significantly suppress the temperature dependence of the drag coefficient of QGP as compared to that of an ideal relativistic system of quarks and gluons. Inclusion of shear and bulk viscosities through the corrections to the thermal phase space factors of the bath particles alters the magnitude of the drag coefficient, and the enhancement is significant at lower temperatures. In the competition between the effects of the EoS and dissipative corrections through phase space factors; the former eventually dictate how the drag coefficient would behave as a function of temperature, and how much quantitatively digress from the ideal case. The observations suggest significant impact of both the realistic equation of state, and the viscosities, on the HQs transport at RHIC and the LHC collision energies.
Heavy quark dynamics in the QGP: and from RHIC to LHC
Nuclear Physics A, 2011
We study the stochastic dynamics of c and b quarks in the hot plasma produced in nucleus-nucleus collisions at RHIC and LHC, providing results for the nuclear modification factor R AA and the elliptic flow coefficient v 2 of the singleelectron spectra arising from their semi-leptonic decays. The initial QQ pairs are generated using the POWHEG code, implementing pQCD at NLO. For the propagation in the plasma we develop a relativistic Langevin equation (solved in a medium described by hydrodynamics) whose transport coefficients are evaluated through a first-principle calculation. Finally, at T c , the heavy quarks are made hadronize and decay into electrons: the resulting spectra are then compared with RHIC results. Predictions for LHC are also attempted.
Heavy quark diffusion in the pre-equilibrium stage of heavy ion collisions
Journal of Physics G: Nuclear and Particle Physics, 2015
The drag and diffusion coefficients of heavy quarks (HQs) have been evaluated in the pre-equilibrium phase of the evolving fireball produced in heavy ion collisions at RHIC and LHC energies. The KLN and classical Yang-Mills spectra have been used for describing the momentum distributions of the gluons produced just after the collisions but before they thermalize. The interaction of the HQs with these gluons has been treated within the framework of perturbative QCD. We have observed that the HQs are dragged almost equally by the kinetically equilibrated and out-of-equilibrium gluonic systems. We have also noticed that the HQs diffusion in the pre-equilibrium gluonic phase is as fast as in the kinetically equilibrated gluons. Moreover, the diffusion is faster in the pre-equilibrium phase than in the chemically equilibrated quark-gluon plasma. These findings may have significant impact on the analysis of experimental results on the elliptic flow and the high momentum suppression of the open charm and beauty hadrons.
Heavy quark transport at RHIC and LHC
Journal of Physics: Conference Series, 2013
We have implemented a Langevin approach for the transport of heavy quarks in the UrQMD hybrid model. The UrQMD hybrid approach provides a realistic description of the background medium for the evolution of relativistic heavy ion collisions. We have used two different sets of drag and diffusion coefficients, one based on a T -Matrix approach and one based on a resonance model for the elastic scattering of heavy quarks within the medium. In case of the resonance model we have investigated the effects of different decoupling temperatures of the heavy quarks from the medium, ranging between 130 MeV and 180 MeV. We present calculations of the nuclear modification factor R AA , as well as of the elliptic flow v 2 in Au+Au collisions at √ s N N = 200 GeV and Pb+Pb collisions at √ s N N = 2.76 TeV. To make our results comparable to experimental data at RHIC and LHC we have implemented a Peterson fragmentation and a quark coalescence approach followed by the semileptonic decay of the D-and B-mesons to electrons. We find that our results strongly depend on the decoupling temperature and the hadronization mechanism. At a decoupling temperature of 130 MeV we reach a good agreement with the measurements at both, RHIC and LHC energies, simultaneously for the elliptic flow v 2 and the nuclear modification factor R AA .
Nonperturbative Heavy-Quark Diffusion in the Quark-Gluon Plasma
Physical Review Letters, 2008
Heavy quarks (charm and bottom) are valuable probes of the hot and dense matter produced in ultrarelativistic heavy-ion collisions: they are produced in initial hard nucleon-nucleon collisions and subsequently interact with the medium consisting of light quarks and gluons. Data on light hadron spectra in 200 AGeV Au-Au collisions at the Relativistic Heavy-Ion Collider (RHIC) have shown that the produced partonic medium can be described by ideal hydrodynamics, suggestive for a strongly interacting quark-gluon plasma (sQGP) : after the collision the medium appears to equilibrate rapidly building up pressure which is associated with the observed collective flow of hadrons. Heavy quarks, due to their large mass, m Q >>T c (T c ≈180 MeV: critical temperature), are particularly sensitive to the microscopic interaction mechanisms underlying the apparent rapid thermalization. At RHIC the measurement of transverse-momentum (p t ) spectra and elliptic flow, v 2 , of non-photonic electrons [3,4] -originating from the decay of open-charm (D) and -bottom mesons (B) -have lead to the conclusion that heavy quarks interact surprisingly strongly with the medium, largely inheriting its collective-flow pattern via the corresponding drag within the medium. These observations indicate large momentum-diffusion coefficients which can not be accounted for in perturbative QCD (pQCD).
Evolution of Hot, Dissipative Quark Matter in Relativistic Nuclear Collisions
Non-ideal fluid dynamics with cylindrical symmetry in transverse direction and longitudinal scaling flow is employed to simulate the space-time evolution of the quark-gluon plasma produced in heavy-ion collisions at RHIC energies. The dynamical expansion is studied as a function of initial energy density and initial time. A causal theory of dissipative fluid dynamics is used instead of the standard theories which are acausal. We compute the parton momentum spectra and HBT radii from two-particle correlation functions. We find that, in non-ideal fluid dynamics, the reduction of the longitudinal pressure due to viscous effects leads to an increase of transverse flow and a decrease of the ratio Rout/RsideR_{out}/R_{side}Rout/Rside as compared to the ideal fluid approximation.
Heavy quark transport in heavy ion collisions at RHIC and LHC within theUrQMD transport model
2012
We have implemented a Langevin approach for the transport of heavy quarks in the UrQMD hybrid model. The UrQMD hybrid approach provides a realistic description of the background medium for the evolution of relativistic heavy ion collisions. We have used two different sets of drag and diffusion coefficients, one based on a T -Matrix approach and one based on a resonance model for the elastic scattering of heavy quarks within the medium. In case of the resonance model we have investigated the effects of different decoupling temperatures of the heavy quarks from the medium, ranging between 130 MeV and 180 MeV. We present calculations of the nuclear modification factor R AA , as well as of the elliptic flow v 2 in Au+Au collisions at √ s N N = 200 GeV and Pb+Pb collisions at √ s N N = 2.76 TeV. To make our results comparable to experimental data at RHIC and LHC we have implemented a Peterson fragmentation and a quark coalescence approach followed by the semileptonic decay of the D-and B-mesons to electrons. We find that our results strongly depend on the decoupling temperature and the hadronization mechanism. At a decoupling temperature of 130 MeV we reach a good agreement with the measurements at both, RHIC and LHC energies, simultaneously for the elliptic flow v 2 and the nuclear modification factor R AA .
Physical Review C, 2016
We have implemented a Langevin approach for the transport of heavy quarks in the UrQMD hybrid model. The UrQMD hybrid approach provides a realistic description of the background medium for the evolution of relativistic heavy ion collisions. We have used two different sets of drag and diffusion coefficients, one based on a T -Matrix approach and one based on a resonance model for the elastic scattering of heavy quarks within the medium. In case of the resonance model we have investigated the effects of different decoupling temperatures of the heavy quarks from the medium, ranging between 130 MeV and 180 MeV. We present calculations of the nuclear modification factor R AA , as well as of the elliptic flow v 2 in Au+Au collisions at √ s N N = 200 GeV and Pb+Pb collisions at √ s N N = 2.76 TeV. To make our results comparable to experimental data at RHIC and LHC we have implemented a Peterson fragmentation and a quark coalescence approach followed by the semileptonic decay of the D-and B-mesons to electrons. We find that our results strongly depend on the decoupling temperature and the hadronization mechanism. At a decoupling temperature of 130 MeV we reach a good agreement with the measurements at both, RHIC and LHC energies, simultaneously for the elliptic flow v 2 and the nuclear modification factor R AA .