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On pseudorapidity distribution and speed of sound in high energy heavy ion collisions based on a new revised Landau hydrodynamic model
We propose a new revised Landau hydrodynamic model to study systematically
the pseudorapidity distributions of charged particles produced in heavy ion
collisions over an energy range from a few GeV to a few TeV per nucleon pair.
The interacting system is divided into three sources namely the central,
target, and projectile sources respectively. The large central source is
described by the Landau hydrodynamic model and further revised by the
contributions of the small target/projectile sources. In the calculation, to
avoid the errors caused by an unapt conversion or non-division, the rapidity
and pseudorapidity distributions are obtained respectively. The modeling
results are in agreement with the available experimental data at relativistic
heavy ion collider (RHIC), large hadron collider (LHC), and other energies for
different centralities. The value of square speed of sound parameter in
different collisions has been extracted by us from the widths of rapidity
distributions. Our results show that, in heavy ion collisions at RHIC and LHC
energies, the central source undergoes through a phase transition from hadronic
gas to quark-gluon plasma (QGP) liquid phase; meanwhile, the target/projectile
sources remain in the state of hadronic gas. The present work confirms that the
QGP is of liquid type rather than that of a gas. The whole region of
participants undergoes through a mixed phase consisting of a large quantity of
(>90%) QGP liquid and a small quantity of (<10%) hadronic gas.Comment: 32 pages, 14 figure
Excitation functions of parameters extracted from three-source (net-)proton rapidity distributions in Au-Au and Pb-Pb collisions over an energy range from AGS to RHIC
Experimental results of the rapidity spectra of protons and net-protons
(protons minus antiprotons) emitted in gold-gold (Au-Au) and lead-lead (Pb-Pb)
collisions, measured by a few collaborations at the alternating gradient
synchrotron (AGS), super proton synchrotron (SPS), and relativistic heavy ion
collider (RHIC), are described by a three-source distribution. The values of
the distribution width and contribution ratio (relative
contribution) of the central rapidity region, and the distribution width
and rapidity shift of the forward/backward rapidity
regions, are then obtained. The excitation function of increases
generally with increase of the center-of-mass energy per nucleon pair
. The excitation function of shows a saturation at
GeV. The excitation function of shows a minimum at
GeV and a saturation at GeV. The
excitation function of increase monotonously with in the considered energy range.Comment: 19 pages, 8 figures, The European Physical Journal A, accepte
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