Physics of the quark-gluon plasma

Some features of the high temperature gluonic matter, such as the break-down of the fundamental group symmetry by the kinetic energy, the screening of test quarks by some unusual gluon states and the explanation of the absence of isolated quarks in the vacuum without the help of infinities are presented in this talk. Special attention is paid to separate the dynamical imput inferred from the numerical results of lattice gauge theory from the kinematics.     

Heavy hadrons in quark-gluon plasma

We use the nonperturbative quark-antiquark potential derived within the Field Correlator Method and the screened Coulomb potential to calculate binding energies and melting temperatures of heavy mesons and baryons in the deconfined phase of quark-gluon plasma.     

Strangeness production in quark-gluon plasma

In this paper it is shown that the strangeness production in quark-gluon plasma might not serve as an experimental signature for the formation of quark-gluon plasma. Our results are completely based on the computer simulation of the plasma. We have taken into account the full three-dimensional hydrodynamic expansion of the plasma.     

Charmonium states in quark-gluon plasma

We discuss how the spectral changes of quarkonia at T _c can reflect the ‘critical’ behaviour of QCD phase transition. Starting from the temperature dependencies of the energy density and pressure from lattice QCD calculation, we extract the temperature dependencies of the scalar and spin-2 gluon condensates near T _c. We also parametrize these changes into the electric and magnetic condensate near T _c. While the magnetic condensate hardly changes across T _c, we find that the electric condensate increases abruptly above T _c. Similar abrupt change is also seen in the scalar condensate. Using the QCD second-order Stark effect and QCD sum rules, we show that these sudden changes induce equally abrupt changes in the mass and width of J/ψ, both of which are larger than 100 MeV at slightly above T _c.      

Experimental test of the flavor independence of the quark-gluon coupling constant

Reconstruction of charged D¹'s produced inclusively in e⁺e?. annihilation at CM energies near 34.4 GeV is accomplished in the decay modes $\text{D}\text{1}{}^{\mathrm{+}}\text{→}\text{D}{}^0\text{π}{}^{\mathrm{+}}\text{→}\text{K}{}^{\mathrm{?}}\text{gp}{}^{\mathrm{+}}\text{π}{}^0\text{π}{}^{\mathrm{+}}\text{and}\text{D}\text{1}{}^{\mathrm{+}}\text{→}\text{D}{}^0\text{π}{}^{\mathrm{+}}\text{→}\text{K}{}^{\mathrm{?}}\text{gp}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{+}}$ and their charge conjugates. Using these and previously reported $\text{D}\text{1}{}^{\mathrm{+}}\text{→}\text{D}{}^0\text{π}{}^{\mathrm{+}}\text{→}\text{K}{}^{\mathrm{?}}\text{gp}{}^{\mathrm{+}}\text{π}{}^{\mathrm{+}}\text{and}\text{D}\text{1}{}^{\mathrm{+}}\text{→}\text{D}{}^0\text{π}{}^{\mathrm{+}}\text{→}\text{K}{}^{\mathrm{?}}\text{gp}{}^{\mathrm{+}}\text{π}{}^{\mathrm{+}}\text{+}\text{missing}\text{π}{}^0$ channels we present evidence for hard gluon bremsstrahlung from charm quarks and show that the ratio of the quark-gluon coupling constant of charm quarks to the coupling constant obtained in the average hadronic event, $\text{α}{}_{\mathrm{<mtext>s</mtext>}}{}^{\mathrm{<mtext>c</mtext>}}\text{α}{}_{\mathrm{rms}}\text{= 100 ± 0.20 ± 1.20}$. Our result provides evidence that the quark-gluon coupling constant is independent of flavor.     

Nonperturbative heavy-quark diffusion in the quark-gluon plasma

We evaluate heavy-quark (HQ) transport properties in a quark-gluon plasma (QGP) within a Brueckner many-body scheme employing interaction potentials extracted from thermal lattice QCD. The in-medium T matrices for elastic charm- and bottom-quark scattering off light quarks in the QGP are dominated by attractive meson and diquark channels which support resonance states up to temperatures of ~1.5T(c). The resulting drag coefficient increases with decreasing temperature, contrary to expectations based on perturbative QCD scattering. Employing relativistic Langevin simulations we compute HQ spectra and elliptic flow in sqrt[s(NN)]=200 GeV Au-Au collisions. A good agreement with electron decay data supports our nonperturbative computation of HQ diffusion, indicative for a strongly coupled QGP.     

Scanning the quark-gluon plasma with charmonium

We suggest the variation of charmonium production rate with Feynman x(F) in heavy ion collisions as a novel and sensitive probe for the properties of the created matter. Final state interactions with the comoving matter create a minimum at x(F) = 0, which is especially deep and narrow if a quark-gluon plasma is formed. While a strong effect is predicted at SPS, at the RHIC energy it overlaps with the expected peak formed by shadowing effects and needs comparison with pA data. We predict a steep dependence on centrality and suggest that this new probe is complementary to the dependence on transverse energy, and is more sensitive to a scenario of final state interactions.     

The evolution of the quark-gluon plasma

We survey the different stages in the evolution of the quark-gluon plasma expected to be produced in high energy nuclear collisions, and we discuss some specific experimental probes for each.     

The evolution of the quark-gluon plasma

We survey the different stages in the evolution of the quark-gluon plasma expected to be produced in high energy nuclear collisions, and we discuss some specific experimental probes for each.     

Apparent thermalization due to plasma instabilities in the quark-gluon plasma

Hydrodynamical modeling of heavy-ion collisions at RHIC suggests that the quark-gluon plasma (QGP) "thermalizes" in a remarkably short time scale, about 0.6 fm/c. We argue that this should be viewed as indicating fast isotropization, but not necessarily complete thermalization, of the nonequilibrium QGP. Non-Abelian plasma instabilities can drive local isotropization of an anisotropic QGP on a time scale which is faster than ordinary perturbative scattering processes. As a result, we argue that theoretical expectations based on weak-coupling analysis are not necessarily in conflict with hydrodynamic modeling of the early part of RHIC collisions, provided one recognizes the key role of non-Abelian plasma instabilities.