513 research outputs found
QGP fireball explosion
We identify the major physics milestones in the development of strange
hadrons as an observable for both the formation of quark-gluon plasma, and of
the ensuing explosive disintegration of deconfined matter fireball formed in
relativistic heavy ion collisions at 160--20A GeV. We describe the physical
properties of QGP phase and show agreement with the expectations based on an
analysis of hadron abundances. We than also demonstrate that the m_t shape of
hadron spectra is in qualitative agreement with the sudden breakup of a
supercooled QGP fireball.Comment: 10 pages, incl. 4 figures J. Phys. G in press; presented at
STRANGENESS2000 International Conference, Berkeley July 200
Dynamics and freeze-out of hadron resonances at RHIC
Yields, rapidity and transverse momentum spectra of ,
, and the meson resonances ,
, and are predicted. Hadronic rescattering leads to a
suppression of reconstructable resonances, especially at low . A mass
shift of the of 10 MeV is obtained from the microscopic simulation, due
to late stage formation in the cooling pion gas.Comment: Proceedings of the Strange Quark Matter 2003, eprint version differs
from published versio
Strangeness Conservation in Hot Nuclear Fireballs
A constraint between thermal fireball parameters arises from the requirement
that the balance of strangeness in a fireball is (nearly) zero. We study the
impact of this constraint on (multi-)strange (anti-)baryon multiplicities and
compare the hadron gas and quark-gluon plasma predictions. We explore the
relation between the entropy content and particle multiplicities and show that
the data are compatible with the quark-gluon plasma hypothesis, but appear to
be inconsistent with the picture of an equilibrated hadron gas fireball. We
consider the implications of the results on the dynamics of evolution and decay
of the particle source.Comment: 35 pages, 11 postscript figures, report PAR/LPTHE/92--2
Viscosity of an ideal relativistic quantum fluid: A perturbative study
We show that a quantized ideal fluid will generally exhibit a small but
non-zero viscosity due to the backreaction of quantum soundwaves on the
background. We use an effective field theory expansion to estimate this
viscosity to first order in perturbation theory. We discuss our results, and
whether this estimate can be used to obtain a more model-independent estimate
of the "quantum bound" on the viscosity of physical systemsComment: Accepted for publication, Phys.Rev.D. Discussion slightly clarified
and extended, references added, error in calculation fixed. COnclusions
unchange
Strangeness and Quark Gluon Plasma
A brief summary of strangeness mile stones is followed by a chemical
non-equilibrium statistical hadronization analysis of strangeness results at
SPS and RHIC. Strange particle production in AA interactions at
\sqrt{s_{NN}}\ge 8.6 GeV can be understood consistently as originating from the
deconfined quark--gluon plasma in a sudden hadronization process. Onset of QGP
formation as function of energy is placed in the beam energy interval 10--30A
GeV/c. Strangeness anomalies at LHC are described.Comment: 30 pages including numerouse figures, tables. Opening Lecture:
Strangeness and Quark Gluon Plasma -- what has been learned so far and where
do we go at SQM2003, North Carolina, March 2003, submitted to J. Phys.
Strangeness enhancement from strong color fields at RHIC
In ultra-relativistic heavy ion collisions, early stage multiple scatterings
may lead to an increase of the color electric field strength. Consequently,
particle production - especially heavy quark (and di-quark) production - is
greatly enhanced according to the Schwinger mechanism. We test this idea via
the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD) for Au+Au
collisions at the full RHIC energy ( AGeV). Relative to p+p
collisions, a factor of 60, 20 and 7 enhancement respectively, for
(), (), and , () is predicted for a model
with increased color electric field strength
Hadronic centrality dependence in nuclear collisions
The kaon number density in nucleus+nucleus and p+p reactions is investigated
for the first time as a function of the initial energy density and
is found to exhibit a discontinuity around =1.3 GeV/fm. This
suggests a higher degree of chemical equilibrium for
1.3 GeV/fm. It can also be interpreted as reflection of the same
discontinuity, appearing in the chemical freeze out temperature (T) as a
function of . The dependence of (u,d,s) hadrons,
whith N the number of participating nucleons, also indicates a high degree of
chemical equilibrium and T saturation, reached at 1.3 GeV/fm.
Assuming that the intermediate mass region (IMR) dimuon enhancement seen by
NA50 is due to open charm (), the following observation can be made:
a) Charm is not equilibrated. b) suppression -unlike
- appears also in S+A collisions, above 1
GeV/fm. c) Both charm and strangeness show a discontinuity near the same
. d) could be formed mainly through coalescence.
e) The enhancement factors of hadrons with u,d,s,c quarks may be connected in a
simple way to the mass gain of these particles if they are produced out of a
quark gluon plasma (QGP). We discuss these results as possible evidence for the
QCD phase transition occuring near 1.3 GeV/fm.Comment: 4 pages, 4 figures, proceedings of Vth International Conference on
Strangeness in Quark Matter, 20-25 July 2000, Berkeley, California. To appear
in Journal of Physics G: Nuclear and Particle Physic
Production Ratios of Strange Baryons from QGP with Diquarks
Assuming that vector and scalar diquarks exist in the Quark-Gluon Plasma near
the critical temporature , baryons can be produced through the processes
of quarks and diquarks forming baryon states. Ratios of different
baryons can be estimated through this method, if such kind of QGP with diquarks
can exists.Comment: Correct some expressions of equation
Scattering of a Klein-Gordon particle by a Woods-Saxon potential
We solve the Klein-Gordon equation in the presence of a spatially
one-dimensional Woods-Saxon potential. The scattering solutions are obtained in
terms of hypergeometric functions and the condition for the existence of
transmission resonances is derived. It is shown how the zero-reflection
condition depends on the shape of the potential.Comment: 10 pages, Revtex. To appear in Phys. Rev.
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