75 research outputs found
Symmetry constraints for the emission angle dependence of Hanbury Brown--Twiss radii
We discuss symmetry constraints on the azimuthal oscillations of two-particle
correlation (Hanbury Brown--Twiss interferometry) radii for non-central
collisions between equal spherical nuclei. We also propose a new method for
correcting in a model-independent way the emission angle dependent correlation
function for finite event plane resolution and angular binning effects.Comment: 8 pages revtex4, 2 tables, no figures. Short Section VI added and
correction algorithm in Section VII made more explicit. Submitted to Physical
Review
Universal Pion Freeze-out Phase-Space Density
Results on the pion freeze-out phase-space density in sulphur-nucleus, Pb-Pb
and pion-proton collisions at CERN-SPS are presented. All heavy-ion reactions
are consistent with the thermal Bose-Einstein distrtibution f=1/(exp(E/T)-1) at
T~120 MeV, modified for expansion. Pion-proton data are also consistent with f,
but at T~180 MeV.Comment: 1 page, 1 figure; 98' report for GSI-Darmstad
Flow effects on the freeze-out phase-space density in heavy ion collisions
The strong longitudinal expansion of the reaction zone formed in relativistic
heavy-ion collisions is found to significantly reduce the spatially averaged
pion phase-space density, compared to naive estimates based on thermal
distributions. This has important implications for data interpretation and
leads to larger values for the extracted pion chemical potential at kinetic
freeze-out.Comment: 5 pages, 3 figures included via epsfig, added discussion of different
transverse density profiles, 1 new figur
Lifetimes and Sizes from Two-Particle Correlation Functions
We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the
two-particle correlation function for azimuthally symmetric expanding sources.
We derive model-independent expressions for the YKP fit parameters and discuss
their physical interpretation. We use them to evaluate the YKP fit parameters
and their momentum dependence for a simple model for the emission function and
propose new strategies for extracting the source lifetime. Longitudinal
expansion of the source can be seen directly in the rapidity dependence of the
Yano-Koonin velocity.Comment: 15 pages REVTEX, 2 figures included, submitted to Phys. Lett. B,
Expanded discussion of disadvantages of standard HBT fit and of Fig.
The relationship between particle freeze-out distributions and HBT radius parameters
The relationship between pion and kaon space-time freeze-out distributions
and the HBT radius parameters in high-energy nucleus-nucleus collisions is
investigated. We show that the HBT radius parameters in general do not reflect
the R.M.S. deviations of the single particle production points. Instead, the
HBT radius parameters are most closely related to the curvature of the
two-particle space-time relative position distribution at the origin. We
support our arguments by studies with a dynamical model (RQMD 2.4).Comment: RevTex, 10 pages including 3 figures. v2: Discussion of the lambda
parameter has been added. PRC, in prin
Heavy-to-light ratios as a test of medium-induced energy loss at RHIC and the LHC
The ratio of nuclear modification factors of high- heavy-flavored mesons
tolight-flavored hadrons (heavy-to-light ratio) is shown to be a sensitive tool
to test medium-induced energy loss at RHIC and LHC energies. Heavy-to-light
ratios of mesons at RHIC in the region GeV, and of and
mesons at the LHC in the region GeV, are proposed for such a test.
Finally, the different contributions to the nuclear modification factor for
electrons at RHIC are analyzed. Preliminary PHENIX and STAR data are compatible
with radiative energy loss provided the contribution of electrons from beauty
decays is small compared to that from charm.Comment: 5 pages, latex, 4 eps figs included using graphicx; to appear in the
proceedings of 18th International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions: Quark Matter 2005 (QM 2005), Budapest, Hungary,
4-9 Aug 200
Bose-Einstein Weights for Event Generators
A simple new algorithm for the calculation of two-particle Bose-Einstein
correlations from classical event generators is derived and discussed.Comment: 4 pages, RevTeX, one ps-figur
Dependence of energy loss of jets on the initial thermodynamic state of deconfined matter at RHIC
The dependence of the radiative energy loss of fast partons on the initial
thermodynamic parameters is studied for deconfined matter to be expected at
RHIC. We demonstrate that the specific QCD radiation pattern with a quadratic
dependence of the energy loss on the propagated distance leads to a strong
increase of the energy loss with increasing initial entropy of deconfined
matter supposed its life-time is less than the average time to pass through the
medium. This is in contrast to a parameterization with constant energy loss per
unit length of propagation. For a sufficiently high initial temperature a
two-regime behavior of the energy loss as a function of the initial parton
momentum occurs. The angular structure of the energy loss of hard jets with
respect to the initial temperature is also discussed for RHIC conditions.Comment: 10 pages with fig
Energy loss in high energy heavy ion collisions from the Hydro+Jet model
We investigate the effect of energy loss of jets in high energy heavy ion
collisions by using a full three-dimensional space-time evolution of a fluid
combined with (mini-)jets that are explicitly evolved in space-time. In order
to fit the pi^0 data for the Au+Au collisions at sqrt(s_{NN}) = 130 GeV, the
space-time averaged energy loss dE/dx(tau <= 3 fm/c) = 0.36 GeV/fm is extracted
within the model. It is found that most energy loss occurs at the very early
time less than 2 fm/c in the QGP phase and that energy loss in the mixed phase
is negligible within our parameterization for jet energy loss. This is a
consequence of strong expansion of the system.Comment: 4 pages, 5 figures; one figure adde
The Ter-Mikayelian Effect on QCD Radiative Energy Loss
The color dielectric modification of the gluon dispersion relation in a dense
QCD medium suppresses both the soft and collinear gluon radiation associated
with jet production. We compute both the longitudinal and transverse plasmon
contributions to the zeroth order in opacity radiative energy loss. This QCD
analog of the Ter-Mikayelian effect in QED leads to reduction of the
energy loss of high transverse momentum charm quarks produced in a QCD plasma
with a characteristic Debye mass GeV.Comment: 18 Pages, 16 Figure
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