Photon polarization as a probe for quark–gluon plasma dynamics

Prospects of measuring polarized photons emitted from a quark–gluon plasma (QGP) are discussed. In particular, the detection of a possible quark spin polarization in a QGP using circularly polarized photons emitted from the plasma is studied. Photons leave the QGP without further interaction and thus provide a primary probe for quark polarization within the QGP. We find that photon polarization cannot solely arise due to a possible QGP momentum space anisotropy, but may be enhanced due to it. In particular, for oblate momentum distributions and high photon energies, quark polarization is efficiently transfered to photon polarization. The role of competing sources of polarized photons in heavy-ion collisions is discussed.     

Refractive index of light and the quark-gluon plasma

The refractive index (RI) of light propagating in a medium of quark-gluon plasma (QGP) is studied. The weakly coupled QGP is studied in the framework of hard-thermal-loop (HTL) perturbation theory, and the strongly coupled one is treated based on the holographic approach. In more realistic setups, the feasibility of observing the optical phenomenon related to the RI of QGP is also discussed.     

Vector bosons in heavy-ion collisions at the LHC

Vector bosons become accessible experimental probes in heavy-ion collisions at the LHC. The capabilities of the LHC experiments to perform their measurement are outlined. The focus is given to their utility to study the possible formation and properties of the Quark Gluon Plasma (QGP) in the most central heavy-ion collisions. Their own sensitivity (if any) to the QGP is discussed. Their interest as references to observe multiple QGP sensitive probes is justified.     

在弛豫时间近似下QGP中夸克输运系数的一种计算

从动力论方程出发,考虑QGP中平均场效应,采用弛豫时问近似,给出了关于QGP输运系数的一种分析方法,推导出QGP中夸克输运系数解析式,讨论了QGP粘滞效应与导热效应.     

Quark—Gluon Plasma in Equilibrium State

The thermodynamic potential of quark-gluon plasma (QGP) in equilibrium state is calculated by finite temperature QCD. The pressure correction of QGP and the critical temperature correction of deconfinement phase transition of hadron are discussed.     

QGP中夸克静色电波的辐射研究

利用QGP中存在德拜屏蔽现象以及高温极限下QGP中夸克的分布函数和色电势,得到QGP中夸克静色电波的辐射功率. 讨论了夸克静色电波的辐射功率与德拜长度λ_D的关系,有助于利用辐射功率研究德拜屏蔽位势.     

Semiclassical Quasilinear Equation of Turbulent QGP and Non-Abelian Quasilinear Diffusion

After the concept of turbulent QGP is introduced, the quasilinear equations for turbulent QGP are given. Starting from the field equation, we still treat the collective modes as plasmons that satisfy a transport equation. Using the quasilinear equations for quarks and gluons and the transport equation for plasmons, the collisionless diffusion is discussed. We obtain the quasilinear drag coefficient and the diffusion coefficient.     

Study on Radiation of the Rrest color Electric Wave of Quarks in QGP

Using the Debye screening in QGP, the disbibudon function and the color electric potential of the quarks at high temperature, the radiated power of the rest color electric wave of the quarks in QGP are obtained. The relation between the radiated power of the rest color electric wave of the quarks and the Dedbye length λ_D is discussed. This will help to study the Debye screening potendal using the radiated Power.     

Status of Quark-Gluon Plasma

I review the current status of the experimental searches for a Quark-Gluon Plasma in heavy ion collisions. The brief introduction covers important results of finite temperature lattice QCD and the intuitive Bjorken picture of Quark-Gluon Plasma (QGP) formation. Global features of the data, such as transverse energy distributions and the various signatures of QGP such asJ/ϕ-suppression, ψ-enhancement as well as thermal dileptons and photons are then discussed.     

Physics around the QCD (tri)critical endpoint and new challenges for femtoscopy

On the basis of exactly solvable models with the tricritical and critical endpoints I discuss the physical mechanism of endpoints formation which is similar to the usual liquids. It is demonstrated that the necessary condition for the transformation of the 1-st order deconfinement phase transition into the 2-nd order phase transition at the (tri)critical endpoint is the vanishing of surface tension coefficient of large/heavy QGP bags. Using the novel model of the confinement phenomenon I argue that the physical reason for the cross-over appearance at low baryonic densities is the negative value of QGP bag surface tension coefficient. This implies the existence of highly non-spherical or, probably, even fractal surfaces of large and heavy bags at and above the cross-over, which, perhaps, can be observed via some correlations. The model with the tricritical endpoint predicts that at the deconfinement transition line the volume (mass) distribution of large (heavy) QGP bags acquires the power law form at the endpoint only, while in the model with the critical endpoint such a power law exists inside the mixed phase. The role of finite width of QGP bags is also discussed.     

QGP Kinetic Equations Beyond the Linear Response Theory

It is shown that the non-Abelian properties? of QGP can be got by studying the kinetic equations for QGP beyond the linear response theory. The non-Abelian interaction of the eigenmodes in QGP is found and two quantities describing the non-Abelian properties of QGP are given.     

Semiclassical Model of Quark—Gluon Plasma

A semiclassical model of a gluon—quark plasma (QGP) is provided. The spinof the quark is described by an antisymmetric tensor S and color charges,and spin tensor are defined as semiclassical numbers. The transport propertiesof QGP in color space and spin space are investigated. The consistency of thesemiclassical model and the quantum models of QGP is discussed.     

The thermodynamic properties of weakly interacting quark-gluon plasma via the one-gluon exchange interaction

The thermodynamic properties of the quark-gluon plasma (QGP), as well as its phase diagram, are calculated as a function of baryon density (chemical potential) and temperature. The QGP is assumed to be composed of the light quarks only, i.e., the up and down quarks, which interact weakly, and the gluons which are treated as they are free. The interaction between quarks is considered in the framework of the one gluon exchange model which is obtained from the Fermi liquid picture. The bag model is used, with fixed bag pressure (B)for the nonperturbative part, and the quantum chromodynamics (QCD) coupling is assumed to be constant, i.e., with no dependence on the temperature or the baryon density. The effect of weakly interacting quarks on the QGP phase diagram are shown and discussed. It is demonstrated that the one-gluon exchange interaction for the massless quarks has considerable effect on the QGP phase diagram and it causes the system to reach to the confined phase at the smaller baryon densities and temperatures. The pressure of excluded volume hadron gas model is also used to find the transition phase diagram. Our results depend on the values of bag pressure and the QCD coupling constant. The latter does not have a dramatic effect on our calculations. Finally, we compare our results with the thermodynamic properties of strange quark matter and the lattice QCD prediction for the QGP transition critical temperature.     

Enhancement of Dileptons with Intermediate Masses Produced in QGP

The production of dileptons in the intermediate mass region in QGP has been studied on the basis of a relativistic hydrodynamic model. Due to the influence of the phase boundary on the evolution of the QGP system and the high initial temperature of the QGP produced at RHIC energies, the quark phase contribution is much more important than that from hadronic interactions and even comparable with that from background sources. It is shown that such an enhancement is a signature for the QGP formation.     

产生在夸克–胶子等离子体中的中等质量双轻子的增强

基于一个相对论流体力学模型,在夸克–胶子等离子体中具有中等质量双轻子的产生被研究.由于相边对夸克–胶子等离子体系统演化的影响和产生在RHIC能量的夸克–胶子等离子体系统有高的初始温度,夸克相的贡献变得比强子相互作用的贡献重要得多,甚至能与本底相比较.它表明这样的增强是夸克–胶子等离子体形成的一种信号.     

QGP中胶子的经典输运方程

建立了夸克胶子等离子体中胶子的经典输运方程, 并讨论了它与胶子的量子输运方程以及它与夸克的经典输运方程之间的关系.     

Quark gluon plasma

Recent trends in the research of quark gluon plasma (QGP) are surveyed and the current experimental and theoretical status regarding the properties and signals of QGP is reported. We hope that the experiments commencing at relativistic heavy-ion collider (RHIC) in 2000 will provide a glimpse of the QGP formation.     

Pion and strangeness puzzles

The dependence of pion and strangeness production on the number of participant nucleons and collision energy is discussed for central A+A collisions. A possible interpretation of the experimental results assuming transition to QGP is sketched within a simple statistical approach.