G. Burau

FINITE T MESON CORRELATIONS AND QUARK DECONFINEMENT

The finite temperature spatial correlation modes in the π and ρ channels are studied with the rainbow-ladder truncated quark Dyson–Schwinger equation and Bethe–Salpeter equation in the Matsubara formalism. To retain the finite range of the effective interaction while facilitating summation over fermion Matsubara modes necessary to ensure continuity at T=0, a separable kernel is used. The model is fixed by T=0 properties and it implements dynamical chiral symmetry breaking and quark confinement. Transition temperatures for deconfinement (Td) and chiral restoration (Tc) are identified. Above and below these transitions we study Mπ(T), fπ(T) and the three-space transverse and longitudinal masses and . We also study the intrinsic T-dependence of the electromagnetic coupling constant gρ(T) and the strong coupling constant gρππ(T). For both this model and a related semi-analyticinfrared dominant model, we analyze the high T behavior of the obtained masses in comparison to the M(T)→2πT behavior found in lattice QCD simulations.

Chiral quark model with infrared cut-off for the description of meson properties in hot matter

Abstract. A simple chiral quark model of the Nambu-Jona-Lasinio (NJL) type with a quark confinement mechanism is constructed for the description of the light-meson sector of QCD at finite temperature. Unphysical quark production thresholds in the NJL model are excluded by an infrared cut-off in the momentum integration within quark loop diagrams. This chiral quark model satisfies the low-energy theorems. Using the vacuum masses and decay widths of π- and ρ-mesons for fixing the model parameters, the properties of the σ-meson are derived. Within the Matsubara formalism, the model is systematically extended to finite temperatures where chiral symmetry restoration due to a dropping constituent quark mass entails a vanishing of the infrared cut-off (deconfinement) at the pion Mott temperature Tc = 186 MeV. Besides the pion mass and weak decay constant, the masses, coupling constants and decay widths of σ- and ρ-mesons in hot matter are investigated. The quark-antiquark decay channel of the light mesons is opened for T > Tc only and becomes particularly strong for the ρ-meson. The two-pion decay channel below Tc has almost constant width for the ρ-meson up to Tc, but for the σ-meson it closes below Tc such that a scalar meson state with vanishing width is obtained as a precursor of the chiral/deconfinement transition.

DYSON-SCHWINGER EQUATION APPROACH TO THE QCD DECONFINEMENT TRANSITION AND J/φ DISSOCIATION

We consider an extension of the finite-temperature Dyson-Schwinger equation (DSE) approach to heavy mesons and quarkonia and apply it to calculate the cross section for the J/Psi breakup reaction J/Psi + pi --> D + D. We study the effects of chiral symmetry restoration in the light quark sector on this process and obtain a critical enhancement of the reaction rate at the chiral/ deconfinement transition. Implications for the kinetics of charmonium production in ultrarelativistic heavy-ion collisions are discussed with particular emphasis on the recently observed anomalous J/Psi suppression as a possible signal for quark matter formation.

Chiral Symmetry Restoration and Anomalous J/ψ Suppression

We investigate the in-medium modification of pseudoscalar and vector mesons within a QCD motivated chiral quark model by solving the Dyson-Schwinger equations for quarks and mesons at finite temperature in the wide mass range from light mesons (π, σρ ) to opencharm mesons (D, D ∗ ). At the chiral/deconfinement phase transition, the quark-antiquark bound states enter the continuum of unbound states and become broad resonances (Mott effect). We calculate the in-medium cross section for charmonium breakup processes due to light hadron impact within a chiral Lagrangian approach and show that the Mott effect for the D-mesons effectively reduces the threshold for charmonium breakup and leads to a step-like behaviour of the reaction rate. This is suggested as an explanation of the anomalous J/ψ suppression phenomenon in the NA50 experiment.

Chiral symmetry restoration and anomalous J/psi suppression

We investigate the in-medium modification of pseudoscalar and vector mesons within a QCD motivated chiral quark model by solving the Dyson-Schwinger equations for quarks and mesons at finite temperature in the wide mass range from light mesons (π, σρ ) to opencharm mesons (D, D ∗ ). At the chiral/deconfinement phase transition, the quark-antiquark bound states enter the continuum of unbound states and become broad resonances (Mott effect). We calculate the in-medium cross section for charmonium breakup processes due to light hadron impact within a chiral Lagrangian approach and show that the Mott effect for the D-mesons effectively reduces the threshold for charmonium breakup and leads to a step-like behaviour of the reaction rate. This is suggested as an explanation of the anomalous J/ψ suppression phenomenon in the NA50 experiment.

Mott effect and J/ψ dissociation at the quark-hadron phase transition

Abstract.We investigate the in-medium modification of pseudoscalar and vector mesons in a QCD-motivated chiral quark model by solving the Dyson-Schwinger equations for quarks and mesons at finite temperature for a wide mass range of meson masses, from light (

Heavy flavour kinetics at the hadronization transition

\pi

J/ψ dissociation and hadron formfactors

,

Mott effect and J / psi dissociation at the quark hadron phase transition

\rho

Chiral Lagrangian approach to the J/psi breakup cross section

) to open-charm (D, D*) states. At the chiral/deconfinement phase transition, the quark-antiquark bound states enter the continuum of unbound states and become broad resonances (hadronic Mott effect). We calculate the in-medium cross-sections for charmonium dissociation due to collisions with light hadrons in a chiral Lagrangian approach, and show that the D- and D*-meson spectral broadening lowers the threshold for charmonium dissociation by