499 research outputs found
Strangeness and the discovery of quark-gluon plasma
Strangeness flavor yield s and the entropy yield S are the observables of the
deconfined quark-gluon state of matter which can be studied in the entire
available experimental energy range at AGS, SPS, RHIC, and, in near future, at
the LHC energy range. We present here a comprehensive analysis of strange, soft
hadron production as function of energy and reaction volume. We discuss the
physical properties of the final state and argue how evidence about the
primordial QGP emerges.Comment: 16 pages: Invited talk at 5th International Conference on Physics and
Astrophysics of Quark Gluon Plasma, February 8 - 12, 2005, Salt Lake City,
Kolkata, India, to appear in: Journal of Physics: Conference Serie
Vacuum Structure and Dark Energy
We consider that the universe is trapped in an excited vacuum state and the
resulting excitation energy provides the observed dark energy. We explore the
conditions under which this situation can arise from physics already known.
Considering the example of how macroscopic QED fields alter the vacuum
structure, we find that the energy scale 1 meV --- 1 eV is particularly
interesting. We discuss how dark energy of this form is accessible to
laboratory experiments.Comment: 5 pages, 2 figures; recognized for Honorable Mention in 2010 Gravity
Research Foundation Awards for Essays on Gravitation, in press with Int. J.
Mod. Phys.
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
Conditions for Confinement and Freeze-Out
Matter implies the existence of a large-scale connected cluster of a uniform
nature. The appearance of such clusters as function of hadron density is
specified by percolation theory. We can therefore formulate the freeze-out of
interacting hadronic matter in terms of the percolation of hadronic clusters.
The resulting freeze-out condition as function of temperature and
baryo-chemical potential interpolates between resonance gas behaviour at low
baryon density and repulsive nucleonic matter at low temperature, and it agrees
well with data.Comment: 9 pages, 5 figure
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.
Quark-Gluon Plasma Fireball
Lattice-QCD results provide an opportunity to model, and extrapolate to
finite baryon density, the properties of the quark-gluon plasma (QGP). Upon
fixing the scale of the thermal coupling constant and vacuum energy to the
lattice data, the properties of resulting QGP equations of state (EoS) are
developed. We show that the physical properties of the dense matter fireball
formed in heavy ion collision experiments at CERN-SPS are well described by the
QGP-EoS we presented. We also estimate the properties of the fireball formed in
early stages of nuclear collision, and argue that QGP formation must be
expected down to 40A GeV in central Pb--Pb interactions.Comment: 10 pages, 9 postscript figures, 1 table, uses revtex, V3: introduced
difference between n_f and n_s; fireball restframe energy corrected,
references added. Publisched version in press Phys. Rev.
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