9 research outputs found
The strange-quark chemical potential as an experimentally accessible "order parameter" of the deconfinement phase transition for finite baryon-density
We consider the change of the strange-quark chemical potential in the phase
diagram of nuclear matter, employing the Wilson loop and scalar quark
condensate order parameters, mass-scaled partition functions and enforcing
flavor conservation. Assuming the region beyond the hadronic phase to be
described by massive, correlated and interacting quarks, in the spirit of
lattice and effective QCD calculations, we find the strange-quark chemical
potential to change sign: from positive in the hadronic phase - to zero upon
deconfinement - to negative in the partonic domain. We propose this change in
the sign of the strange-quark chemical potential to be an experimentally
accessible order parameter and a unique, concise and well-defined indication of
the quark-deconfinement phase transition in nuclear matter.Comment: 22 pages, 14 figures within text, 2 figures(6,B3) as separate files.
To be published in J.Phys.G: Nucl.&Part.Phys. G28 (2002
Medium effects in high energy heavy-ion collisions
The change of hadron properties in dense matter based on various theoretical
approaches are reviewed. Incorporating these medium effects in the relativistic
transport model, which treats consistently the change of hadron masses and
energies in dense matter via the scalar and vector fields, heavy-ion collisions
at energies available from SIS/GSI, AGS/BNL, and SPS/CERN are studied. This
model is seen to provide satisfactory explanations for the observed enhancement
of kaon, antikaon, and antiproton yields as well as soft pions in the
transverse direction from the SIS experiments. In the AGS heavy-ion
experiments, it can account for the enhanced ratio, the difference
in the slope parameters of the and transverse kinetic energy
spectra, and the lower apparent temperature of antiprotons than that of
protons. This model also provides possible explanations for the observed
enhancement of low-mass dileptons, phi mesons, and antilambdas in heavy-ion
collisions at SPS energies. Furthermore, the change of hadron properties in hot
dense matter leads to new signatures of the quark-gluon plasma to hadronic
matter transition in future ultrarelativistic heavy-ion collisions at RHIC/BNL.Comment: RevTeX, 65 pages, including 25 postscript figures, invited topical
review for Journal of Physics G: Nuclear and Particle Physic
Lambda production in central Pb+Pb collisions at CERN-SPS energies
In this paper we present recent results from the NA49 experiment for
and hyperons produced in central Pb+Pb collisions at
40, 80 and 158 AGeV. Transverse mass spectra and rapidity distributions
for are shown for all three energies. The shape of the rapidity
distribution becomes flatter with increasing beam energy. The multiplicities at
mid-rapidity as well as the total yields are studied as a function of collision
energy including AGS measurements. The ratio at mid-rapidity and
in 4 has a maximum around 40 AGeV. In addition,
rapidity distributions have been measured at 40 and 80 AGeV, which
allows to study the / ratio.Comment: SQM proceedings. J. Phys. G: Nucl. Part. Phys.: submitte
Strange particle production in nuclear collisions at 200-GeV per nucleon
Multiplicities and spectra of strange particles ( andK− produced in central32S+S,32S+Ag and32S+Au collisions at 200 GeV per nucleon are presented and compared with data on strange particle production in protonnucleus and nucleon-nucleon interactions. It is shown that strangeness production in32S+Ag collisions is enhanced by a factor of two, similar to that found previously in central32S+S collisions
Neutral strange particle production in sulphur sulphur and proton sulphur collisions at 200 GeV/nucleon
Charged particle production in proton-, deuteron-, oxygen- and sulphur-nucleus collisions at 200 GeV per nucleon
The transverse momentum and rapidity distributions of net protons and
negatively charged hadrons have been measured for minimum bias
proton-nucleus and deuteron-gold interactions, as well as central
oxygen-gold and sulphur-nucleus collisions at 200 GeV per nucleon. The
rapidity density of net protons at midrapidity in central
nucleus-nucleus collisions increases both with target mass for sulphur
projectiles and with the projectile mass for a gold target. The shape of
the rapidity distributions of net protons forward of midrapidity for
d+Au and central S+Au collisions is similar. The average rapidity loss
is larger than 2 units of rapidity for reactions with the gold target.
The transverse momentum spectra of net protons for all reactions can be
described by a thermal distribution with ‘temperatures’ between 145+/-11
MeV (p+S interactions) and 244+/-43 MeV (central S+Au collisions). The
multiplicity of negatively charged hadrons increases with the mass of
the colliding system. The shape of the transverse momentum spectra of
negatively charged hadrons changes from minimum bias p+p and p+S
interactions to p+Au and central nucleus-nucleus collisions. The mean
transverse momentum is almost constant in the vicinity of midrapidity
and shows little variation with the target and projectile masses. The
average number of produced negatively charged hadrons per participant
baryon increases slightly from p+p, p+A to central S+S, Ag collisions