31,300 research outputs found
Interferometry signatures for QCD first-order phase transition in heavy ion collisions at GSI-FAIR energies
Using the technique of quantum transport of the interfering pair we examine
the Hanbury-Brown-Twiss (HBT) interferometry signatures for the
particle-emitting sources of pions and kaons produced in the heavy ion
collisions at GSI-FAIR energies. The evolution of the sources is described by
relativistic hydrodynamics with the system equation of state of the first-order
phase transition from quark-gluon plasma (QGP) to hadronic matter. We use
quantum probability amplitudes in a path-integral formalism to calculate the
two-particle correlation functions, where the effects of particle decay and
multiple scattering are taken into consideration. We find that the HBT radii of
kaons are smaller than those of pions for the same initial conditions. Both the
HBT radii of pions and kaons increase with the system initial energy density.
The HBT lifetimes of the pion and kaon sources are sensitive to the initial
energy density. They are significantly prolonged when the initial energy
density is tuned to the phase boundary between the QGP and mixed phase. This
prolongations of the HBT lifetimes of pions and kaons may likely be observed in
the heavy ion collisions with an incident energy in the GSI-FAIR energy range.Comment: 16 pages, 4 figure
Heavy flavor kinetics at the hadronization transition
We investigate the in-medium modification of the charmonium breakup processes
due to the Mott effect for light (pi, rho) and open-charm (D, D*)
quark-antiquark bound states at the chiral/deconfinement phase transition. The
Mott effect for the D-mesons effectively reduces the threshold for charmonium
breakup cross sections, which is suggested as an explanation of the anomalous
J/psi suppression phenomenon in the NA50 experiment. Further implications of
finite-temperature mesonic correlations for the hadronization of heavy flavors
in heavy-ion collisions are discussed.Comment: 4 pages, 2 figures, Contribution to SQM2001 Conference, submitted to
J. Phys.
Heavy Quarkonia and Quark Drip Lines in Quark-Gluon Plasma
Using the potential model and thermodynamical quantities obtained in lattice
gauge calculations, we determine the spontaneous dissociation temperatures of
color-singlet quarkonia and the `quark drip lines' which separate the region of
bound states from the unbound region. The dissociation temperatures
of and in quenched QCD are found to be 1.62 and
respectively, in good agreement with spectral function analyses. The
dissociation temperature of in full QCD with 2 flavors is found to be
1.42. For possible bound quarkonium states with light quarks, the
characteristics of the quark drip lines severely limit the stable region close
to the phase transition temperature. Bound color-singlet quarkonia with light
quarks may exist very near the phase transition temperature if their effective
quark mass is of the order of 300-400 MeV and higher.Comment: 8 pages, 2 figures, in LaTex, invited talk presented at the
International Conference on Strangeness in Quark Matter, UCLA, March 26-31,
200
Color mixing in high-energy hadron collisions
The color mixing of mesons propagating in a nucleus is studied with the help
of a color-octet Pomeron partner present in the two-gluon model of the Pomeron.
For a simple model with four meson-nucleon channels, color mixings are found to
be absent for pointlike mesons and very small for small mesons. These results
seem to validate the absorption model with two independent color components
used in recent analyses of the nuclear absorption of mesons produced
in nuclear reactions.Comment: 3 journal-style page
J/Psi Propagation in Hadronic Matter
We study J/ propagation in hot hadronic matter using a four-flavor
chiral Lagrangian to model the dynamics and using QCD sum rules to model the
finite size effects manifested in vertex interactions through form factors.
Charmonium breakup due to scattering with light mesons is the primary
impediment to continued propagation. Breakup rates introduce nontrivial
temperature and momentum dependence into the J/ spectral function.Comment: 6 Pages LaTeX, 3 postscript figures. Proceedings for Strangeness in
Quark Matter 2003, Atlantic Beach, NC, March 12-17, 2003; minor corrections
in version 2, to appear in J. Phys.
The Utilization of Heat Exchangers for Energy Conservation in Air Conditioning
This paper investigates the characteristics of heat exchanger (HPHE) as an efficient
coolness recovery unit in air conditioning through experimental studies. It was conducted
under a multiple-nozzle code tester based on the ASHRAE standards. The wind tunnel
was subjected to airflow with considerable variation in its inlet air temperature. Among
the factors being investigated are the air velocity, inlet and outlet air temperatures,
overall efficiency and the number of rows in longitudinal direction. The data obtained
were compared with the results predicted by previous theoretical studies. Good agreement
was observed
Exploring Early Parton Momentum Distribution with the Ridge from the Near-Side Jet
In a central nucleus-nucleus collision at high-energies, medium partons
kicked by a near-side jet acquire a momentum along the jet direction and
subsequently materialize as the observed ridge particles. They carry direct
information on the early parton momentum distribution which can be extracted by
using the ridge data for central AuAu collisions at \sqrt{s_{NN}}=200 GeV. The
extracted parton momentum distribution has a thermal-like transverse momentum
distribution but a non-Gaussian, relatively flat rapidity distribution at
mid-rapidity with sharp kinematic boundaries at large rapidities that depend on
the transverse momentum.Comment: In Proceedings of 20th International Conference on Ultra-Relativistic
Nucleus Nucleus Collisions, Jaipur, India, Feb. 4-10, 200
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