316 research outputs found
Effects of Collective Potentials on Pion Spectra in Relativistic Heavy Ion Collisions
The effect of collective potentials on pion spectra in ultrarelativistic
heavy ion collisions is investigated. We find the effect of these potential to
be very small, too small to explain the observed enhancement at low transverse
momenta. (7 figures, bill be send on request)Comment: 11 page
Hydrodynamical assessment of 200 AGeV collisions
We are analyzing the hydrodynamics of 200 A GeV S+S collisions using a new
approach which tries to quantify the uncertainties arising from the specific
implementation of the hydrodynamical model. Based on a previous
phenomenological analysis we use the global hydrodynamics model to show that
the amount of initial flow, or initial energy density, cannot be determined
from the hadronic momentum spectra. We additionally find that almost always a
sizeable transverse flow deve- lops, which causes the system to freeze out,
thereby limiting the flow velocity in itself. This freeze-out dominance in turn
makes a distinction between a plasma and a hadron resonance gas equation of
state very difficult, whereas a pure pion gas can easily be ruled out from
present data. To complete the picture we also analyze particle multiplicity
data, which suggest that chemical equilibrium is not reached with respect to
the strange particles. However, the over- population of pions seems to be at
most moderate, with a pion chemical potential far away from the Bose
divergence.Comment: 19 pages, 11 figs in separate uuencoded file, for LateX, epsf.tex,
dvips, TPR-94-5 and BNL-(no number yet
Boundary and Coulomb Effects on Boson Systems in High-Energy Heavy-Ion Collisions
The boundary of a boson system plays an important role in determining the
momentum distribution of the bosons. For a boson system with a cylindrical
boundary, the momentum distribution is enhanced at high transverse momenta but
suppressed at low transverse momenta, relative to a Bose-Einstein distribution.
The boundary effects on systems of massless gluons and massive pions are
studied. For gluons in a quark-gluon plasma, the presence of the boundary may
modify the signals for the quark-gluon plasma. For pions in a pion system in
heavy-ion collisions, Coulomb final-state interactions with the nuclear
participants in the vicinity of the central rapidity region further modify the
momentum distribution at low transverse momenta. By including both the boundary
effect and the Coulomb final-state interactions we are able to account for the
behavior of the transverse momentum spectrum observed in many
heavy-ion experiments, notably at low transverse momenta.Comment: 15 pages Postscript uuencoded tar-comprssed file, 9 Postscript
figures uuencoded tar-compressed fil
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