1,936 research outputs found
Particle dependence of elliptic flow in Au+Au collisions at 200 GeV
The elliptic flow parameter () for and
has been measured at mid-rapidity in Au + Au collisions at
GeV by the STAR collaboration. The values for both
and saturate at moderate , deviating
from the hydrodynamic behavior observed in the lower region. The
saturated values and the scales where the deviation begins are
particle dependent. The particle-type dependence of shows features
expected from the hadronization of a partonic ellipsoid by coalescence of
co-moving quarks. These results will be discussed in relation to the nuclear
modification factor () which has also been measured for and
by the STAR collaboration.Comment: 6 pages, 3 figures, Strange Quark Matter 2003 Conference (SQM 2003):
updated with 2 figures from original talk that did not appear in the journa
Reconstructed Jets at RHIC
To precisely measure jets over a large background such as pile up in high
luminosity p+p collisions at LHC, a new generation of jet reconstruction
algorithms is developed. These algorithms are also applicable to reconstruct
jets in the heavy ion environment where large event multiplicities are
produced. Energy loss in the medium created in heavy ion collisions are already
observed indirectly via inclusive hadron distributions and di-hadron
correlations. Jets can be used to study this energy loss in detail with reduced
biases. We review the latest results on jet-medium interactions as seen in A+A
collisions at RHIC, focusing on the recent progress on jet reconstruction in
heavy ion collisions.Comment: Proceedings for the 26th Winter Workshop on Nuclear Dynamic
Recent Results on Strangeness Production at RHIC
Due to its large acceptance, the STAR experiment has acquired a wealth of
data on strangeness production for a variety of collisions systems and
energies, from p+p to Au+Au. By using the yields and spectra, we address the
evolution of the bulk system, including strangeness enhancement and the flavour
dependence of radial and elliptic flow. Utilising the fact that we can identify
strange baryons and mesons, we investigate different hadronization mechanisms
in the intermediate and high p regions. The ratios of the particle
yields, measured to high p, are used to further investigate the range and
applicability of the previously reported anomalous baryon production. We also
study two-particle azimuthal correlations of identified particles in order to
investigate any flavour dependence of jet fragmentation in the available
p range. Data was presented for a number of different collision systems
and energies.Comment: Proceedings of SQM'06 Conference, LA, 2006 (submitted to J. Phys. G
meson production in = 200 GeV Au+Au and pp collisions at RHIC
We present the results for the measurement of meson production in
= 200 GeV Au+Au and pp collisions at the Relativistic Heavy Ion
Collider (RHIC). Using the event mixing technique, spectra and yields are
obtained from the decay channel for different centrality
bins in Au+Au collisions and in pp collisions. We observe that the spectrum
shape in Au+Au collisions depends weakly on the centrality and the shape of the
spectrum in pp collisions is significantly different from that in Au+Au
collisions. In Au+Au collisions, the extracted yield of meson is flat as
a function of rapidity; The of , extracted from the fit function
to the spectra, shows a different behavior as a function of centrality than
that of , and Comment: Proceedings for the 7th International Conference on Strangeness in
Quark Matte
Strongly Intensive Measures for Multiplicity Fluctuations
The recently proposed two families of strongly intensive measures of
fluctuations and correlations are studied within Hadron-String-Dynamics (HSD)
transport approach to nucleus-nucleus collisions. We consider the measures
and for kaon and pion multiplicities in Au+Au
collisions in a wide range of collision energies and centralities. These
strongly intensive measures appear to cancel the participant number
fluctuations. This allows to enlarge the centrality window in the analysis of
event-by-event fluctuations up to at least of 10% most central collisions. We
also present a comparison of the HSD results with the data of NA49 and STAR
collaborations. The HSD describes reasonably well. However, the
HSD results depend monotonously on collision energy and do not reproduce the
bump-deep structure of observed from the NA49 data in the
region of the center of mass energy of nucleon pair
GeV. This fact deserves further studies. The origin of this `structure' is not
connected with simple geometrical or limited acceptance effects, as these
effects are taken into account in the HSD simulations
Hard and soft probe - medium interactions in a 3D hydro+micro approach at RHIC
We utilize a 3D hybrid hydro+micro model for a comprehensive and consistent
description of soft and hard particle production in ultra-relativistic
heavy-ion collisions at RHIC. In the soft sector we focus on the dynamics of
(multi-)strange baryons, where a clear strangeness dependence of their
collision rates and freeze-out is observed. In the hard sector we study the
radiative energy loss of hard partons in a soft medium in the multiple soft
scattering approximation. While the nuclear suppression factor does
not reflect the high quality of the medium description (except in a reduced
systematic uncertainty in extracting the quenching power of the medium), the
hydrodynamical model also allows to study different centralities and in
particular the angular variation of with respect to the reaction
plane, allowing for a controlled variation of the in-medium path-length.Comment: 5 pages, 4 figures, Quark Matter 2006 proceedings, to appear in
Journal of Physics
Probing jet properties via two particle correlation method
The formulae for calculating jet fragmentation momentum, , and conditional yield are discussed in
two particle correlation framework. Additional corrections are derived to
account for the limited detector acceptance and inefficiency, for cases when
the event mixing technique is used. The validity of our approach is confirmed
with Monte-carlo simulation.Comment: Proceeding for HotQuarks2004 conference. 11 pages, 8 figures,
corrected for typo
Space-time analysis of reaction at RHIC
Space-time information about the Au-Au collisions produced at RHIC are key
tools to understand the evolution of the system and especially assess the
presence of collective behaviors. Using a parameterization of the system's
final state relying on collective expansion, we show that pion source radii can
be tied together with transverse mass spectra and elliptic flow within the same
framework. The consistency between these different measures provide a solid
ground to understand the characteristics of collective flow and especially the
possible peculiar behavior of particles such as Xi, Omega or phi. The validity
of the short time scales that are extracted from fits to the pion source size
is also addressed. The wealth of new data that will soon be available from
Au-Au collisions at sqrt{s_{NN}} = 200 GeV, will provide a stringet test of the
space-time analysis framework developped in these proceedings.Comment: Invited talk given at the SQM2003 conference (March 2003), to be
published in Journal of Physics G. 10 pages, 3 figure
Heavy flavor production in pA collisions
Heavy quark production in high-energy proton-nucleus (pA) collisions is
described in the framework of the Color Glass Condensate. kT factorization is
broken even at leading order albeit a more general factorization in pA holds at
this order in terms of 2, 3 and 4 point correlators of Wilson lines in the
nuclear target. The x-evolution of these correlators is computed in the large A
and large N mean field limit of the Balitsky-Kovchegov equation. We show
results for heavy quark production at RHIC and LHC energies.Comment: Talk given at QM2006. 4
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