392 research outputs found
Hadron Mass Spectrum from Lattice QCD
Finite temperature lattice simulations of quantum chromodynamics (QCD) are
sensitive to the hadronic mass spectrum for temperatures below the "critical"
temperature T_c ~ 160 MeV. We show that a recent precision determination of the
QCD trace anomaly shows evidence for the existence of a large number of hadron
states beyond those known from experiment. The lattice results are well
represented by an exponentially growing hadron mass spectrum up to a
temperature T = 155 MeV. Using simple parametrizations we show how one may
estimate the total spectral weight in these yet undermined states
Hadronic Ratios and the Number of Projectile Participants. Thermal hadron production in Si-Au collisions
We investigate the dependence of hadronic ratios on the number of projectile
participants using a thermal model incorporating exact baryon number and
strangeness conservation. A comparison is made with results from
collisions obtained at the BNL-AGS.Comment: 5 pages LaTeX2e, 4 figures in Postscript forma
Aspects of thermal strange quark production: the deconfinement and chiral phase transitions
We study the gluonic sector of the three-flavor PNJL model by obtaining the
adjoint Polyakov loop and the gluon distribution function in the mean-field
approximation. Besides, we explore the thermal strange quark pair-production
processes, and , with the aid of
the three-flavor PNJL model. The results help us identify the temperature where
the gluonic contribution to the production rate becomes dominant, which is an
innovative phenomenon compared with the result obtained in free perturbation
theory.Comment: 4 pages, 2 figures, final version - To appear in the conference
proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
A New Phase of Matter: Quark-Gluon Plasma Beyond the Hagedorn Critical Temperature
I retrace the developments from Hagedorn's concept of a limiting temperature
for hadronic matter to the discovery and characterization of the quark-gluon
plasma as a new state of matter. My recollections begin with the transformation
more than 30 years ago of Hagedorn's original concept into its modern
interpretation as the "critical" temperature separating the hadron gas and
quark-gluon plasma phases of strongly interacting matter. This was followed by
the realization that the QCD phase transformation could be studied
experimentally in high-energy nuclear collisions. I describe here my personal
effort to help develop the strangeness experimental signatures of quark and
gluon deconfinement and recall how the experimental program proceeded soon to
investigate this idea, at first at the SPS, then at RHIC, and finally at LHC.
As it is often the case, the experiment finds more than theory predicts, and I
highlight the discovery of the "perfectly" liquid quark-gluon plasma at RHIC. I
conclude with an outline of future opportunities, especially the search for a
critical point in the QCD phase diagram.Comment: To appear in {\em Melting Hadrons, Boiling Quarks} by Rolf Hagedorn
and Johan Rafelski (editor), Springer Publishers, 2015 (open access
Results from the Relativistic Heavy Ion Collider
We describe the current status of the heavy ion research program at the
Relativistic Heavy Ion Collider (RHIC). The new suite of experiments and the
collider energies have opened up new probes of the medium created in the
collisions. Our review focuses on the experimental discoveries to date at RHIC
and their interpretation in the light of our present theoretical understanding
of the dynamics of relativistic heavy ion collisions and of the structure of
strongly interacting matter at high energy density.Comment: 47 pages, 10 figures, submitted to Annual Review of Nuclear and
Particle Science. The authors invite and appreciate feedback about possible
errors and/or inconsistencies in the manuscrip
Unified Description of Freeze-Out Parameters in Relativistic Heavy Ion Collisions
It is shown that the chemical freeze-out parameters obtained at CERN/SPS,
BNL/AGS and GSI/SIS energies all correspond to a unique value of 1 GeV per
hadron in the local rest frame of the system, independent of the beam energy
and of the target and beam particles.Comment: revtex, 1 figur
Quantum Decoherence, Entropy and Thermalization in Strong Interactions at High Energy
Entropy is generated in high-multiplying events by a dynamical separation of
strongly interacting systems into partons and unobservable environment modes
(almost constant field configurations) due to confinement.Comment: 45 pages, 2 figure
On the Thermodynamics of Hot Hadronic Matter
The equation of state of hot hadronic matter is obtained, by taking into
account the contribution of the massive states with the help of the resonance
spectrum justified by the authors in previous papers. This
equation of state is in agreement with that provided by the low-temperature
expansion for the pion intracting gas. It is shown that in this picture the
deconfinement phase transition is absent, in agreement with lattice gauge
calculations which show the only phase transition of chiral symmetry
restoration. The latter is modelled with the help of the restriction of the
number of the effective degrees of freedom in the hadron phase to that of the
microscopic degrees of freedom in the quark-gluon phase, through the
corresponding truncation of the hadronic resonance spectrum, and the decrease
of the effective hadron masses with temperature, predicted by Brown and Rho.
The results are in agreement with lattice gauge data and show a smooth
crossover in the thermodynamic variables in a temperature range MeV.Comment: 21 pages, LaTeX, 3 postscript figure
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