838 research outputs found
Thermal Equilibration and Expansion in Nucleus-Nucleus Collision at the AGS
The rather complete data set of hadron yields from central Si + A collisions
at the Brookhaven AGS is used to test whether the system at freeze-out is in
thermal and hadro-chemical equilibrium. Rapidity and transverse momentum
distributions are discussed with regards to the information they provide on
hydrodynamic flow.Comment: 11 pages + 2 uuencoded figure
Nuclear Transparency in Heavy Ion Collisions at 14.6 GeV/nucleon
The probability of a projectile nucleon to traverse a target nucleus without
interaction is calculated for central Si-Pb collisions and compared to the data
of E814. The calculations are performed in two independent ways, via Glauber
theory and using the transport code UrQMD. For central collisions Glauber
predictions are about 30 to 50% higher than experiment, while the output of
UrQMD does not show the experimental peak of beam rapidity particles.Comment: 9 pages, 4 figures. submitted to Nucl. Phys.
Soft Open Charm Production in Heavy-Ion Collisions
Effects of strong longitudinal color electric fields (SCF) on the open charm
production in nucleus-nucleus (A + A) collisions at 200A GeV are investigated
within the framework of the HIJING-BBbar v2.0 model. A three fold increase of
the effective string tension due to in medium effects in A + A collisions,
results in a sizeable (60-70 percents) enhancement of the total charm
production cross sections. The nuclear modification factors show a suppression
at moderate transverse momentum consistent with RHIC data. At Large Hadron
Collider energies the model predicts an increase of total charm production
cross sections by approximately an order of magnitude.Comment: 5 pages, 3 figures, submitted to Phys. Rev. Let
Neutral pion production with respect to reaction plane in Au+Au collisions at RHIC-PHENIX
It has been observed that the yield of neutral pions at high transverse
momentum (pT 5 GeV/c) region is strongly suppressed in central Au+Au
collisions at Relativistic Heavy Ion Collider (RHIC), compared to the one
expected in p+p collisions. This suppression may be due to an energy loss of
hard scattered partons in the medium (jet quenching), that results in a
decrease of the yield at a given pT. The magnitude of the suppression would
depend on the path length of scattering partons in the medium, and therefore is
associated with azimuthal angle from reaction plane in non-central collisions.
Studying the path length dependence of energy loss would give additional
information on understanding the energy loss mechanism. We discuss the parton
energy loss mechanism using the nuclear modification factor () of
neutral pion with respect to reaction plane. A new reaction plane detector was
installed in the PHENIX detector in RHIC Year-7 run, and improved the reaction
plane resolution. More precise measurement of the hadron suppression with
respect to path length is expected using the detector. I will report about
analysis status of neutral pion production in Au+Au collisions at
GeV.Comment: 4 pages, 5 figures, Proceedings of the 20th International Conference
on Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008",
Jaipur, India, February 4-10, 200
Phase-space density in heavy-ion collisions revisited
We derive the phase space density of bosons from a general boson
interferometry formula.
We find that the phase space density is connected with the two-particles and
the single particle density distribution functions. If the boson density is
large, the two particles density distribution function can not be expressed as
a product of two single particle density distributions. However, if the boson
density is so small that two particles density distribution function can be
expressed as a product of two single particle density distributions, then
Bertsch's formula is recovered. For a Gaussian model, the effects of
multi-particles Bose-Einstein correlations on the mean phase space density are
studied.Comment: 18 Pages, Four eps files, EPJC in Pres
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