139 research outputs found
Mott dissociation of D-mesons at the chiral phase transition and anomalous J/Psi suppression
We investigate the in-medium modification of the charmonium breakup processes
due to the Mott-effect for D-mesons at the chiral phase transition. A model
calculation for the process J/Psi+pi --> D+D^*+ h.c. is presented which
demonstrates that threshold effects in the thermal averaged breakup cross
section can be explained as a Mott transition where final state quark-antiquark
bound states enter the continuum of resonant states at the QCD phase
transition. Applications to heavy-ion collisions within a modified Glauber
model scenario and the phenomenon of anomalous J/ suppression in the CERN
NA50 experiment are addressed.Comment: 5 pages, 4 figures, uses JHEP.cls styl
Pseudorapidity shape of elliptic flow as signature for fast equilibration in relativistic heavy-ion collisions at energies up to sqrt(s) = 200 GeV
The implications of parton recombination processes on the dynamics of
ultrarelativistic heavy-ion reactions are investigated. To do so, the
quark-gluon string transport model has been extended for partonic recombination
and fusion processes. Parton recombination leads to short equilibration times
and improves significantly on the theoretical description of measured directed
and elliptic flow, i.e., v_1 and v_2, distributions in Au+Au collisions at
sqrt(s) = 200 GeV, in particular what concerns their pseudorapidity dependence.
The shape of v_2(eta) is found to be closely related to fast thermalization.Comment: 7 pages (revtex4) with 4 figures, v3: substantially extended
description and discussion of the model and its results, accepted for
publication in Phys. Rev.
Chiral quark model with infrared cut-off for the description of meson properties in hot matter
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 \pi- and
\rho-mesons for fixing the model parameters, the properties of the \sigma-
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 T_c=186 MeV. Besides of the pion
mass and weak decay constant, the masses, coupling constants and decay widths
of \sigma- and \rho-mesons in hot matter are investigated. The quark-antiquark
decay channel of the light mesons is opened for T>T_c only and becomes
particularly strong for the \rho- meson. The two-pion decay channel below T_c
has almost constant width for the \rho- meson up to T_c, but for the
\sigma-meson it closes below T_c such that a scalar meson state with vanishing
width is obtained as a precursor of the chiral/deconfinement transition.Comment: Latex file, 23 pages, 7 figure
Mott Effect and J/Psi Dissociation at the Quark-Hadron Phase Transition
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 (pi, rho) 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 (the 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 pi and rho meson impact. This leads to a step-like enhancement
in the reaction rate. We suggest that this mechanism for enhanced charmonium
dissociation may be the physical mechanism underlying the anomalous J/Psi
suppression observed by NA50.Comment: 3 pages, 3 figures, uses EPJ style (included), contribution to the
Proceedings of the International Conference on Quark Nuclear Physics, June 9
- 14, 2002, Juelich, Germany; 1 figure added, text adde
Hadronic Spectral Function and Charm Meson Production
At the chiral restoration/deconfinement transition, most hadrons undergo a
Mott transition from being bound states in the confined phase to resonances in
the deconfined phase. We investigate the consequences of this qualitative
change in the hadron spectrum on final state interactions of charmonium in hot
and dense matter, and show that the Mott effect for D-mesons leads to a
critical enhancement of the J/Psi dissociation rate. Anomalous J/Psi
suppression in the NA50 experiment is discussed as well as the role of the Mott
effect for the heavy flavor kinetics in future experiments at the LHC. The
status of our calculations of hadron-hadron cross sections using the quark
interchange and chiral Lagrangian approaches is reviewed, and an Ansatz for a
unification of these schemes is given.Comment: 12 pages, 6 figures, Proceedings of the Budapest'02 Workshop on Quark
& Hadron Dynamics, Budapest, Hungary, March 3-7, 200
Workshops Quark Matter in Astro- and Particle Physics & Dynamical Aspects of the QCD Phase Transition
These proceedings contain research results presented during the Workshops "Quark Matter in Astro- and Particle Physics" held at the University of Rostock, November 27-29, 2000 and "Dynamical Aspects of the QCD Phase Transition" held at the ECT* in Trento, March 12-15, 2001
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