2,352 research outputs found
Multi-strange baryon elliptic flow in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV measured with the ALICE detector
We present the results on elliptic flow with multi-strange baryons produced
in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV. The analysis is performed with
the ALICE detector at LHC. Multi-strange baryons are reconstructed via their
decay topologies and the v_2 values are analyzed with the two-particle scalar
product method. The p_T differential v_2 values are compared to the VISH2+1
model calculation and to the STAR measurements at 200 GeV in Au+Au collisions.
We found that the model describes \Xi and \Omega v_2 measurements within
experimental uncertainties. The differential flow of \Xi and \Omega is similar
to the STAR measurements at 200 GeV in Au+Au collisions.Comment: Prepared for the Proceedings of the International Conference on
"Critical Point and Onset of Deconfinement - CPOD 2011", Wuhan, November
7-11, 201
Measurements of high identified particles and in GeV Au+Au collisions by PHENIX
The and of pions, kaons and protons have been measured by
PHENIX in 200 GeV Au+Au collisions up to 6 GeV/c and 4 GeV/c,
respectively. The of all these identified particles have been found to
scale with the number of constituent quarks and all these particles have a
similar / ratio which is close to 0.9. The scaling behavior
of is studied at high- and a deviations from the universal scaling
is observed for transverse kinetic energy () higher than 1 GeV.Comment: 4 pages, 3 figures, proceedings of 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008),
Jaipur, India, 04-10 Feb 200
Enhanced Event-by-Event Fluctuations in Pion Multiplicity as a Signal of Disoriented Chiral Condensates at RHIC
The factorial moments of the pion multiplicity distributions are calculated
with HIJING and UrQMD and found to be independent of the pT range included, in
contrast to recent simulations with the linear sigma model which leads to large
enhancements for pions with transverse kinetic energies below 200 MeV. This
supports the use of the ratio of the factorial moments of low and high pT pions
as a signal of ``new'' physics at low momentum scales, such as the formation of
disoriented chiral condensates.Comment: 4 pages total, incl 4 eps figures ([email protected]
Charge dependent azimuthal correlations in Pb--Pb collisions at TeV
Separation of charges along the extreme magnetic field created in non-central
relativistic heavy--ion collisions is predicted to be a signature of local
parity violation in strong interactions. We report on results for charge
dependent two particle azimuthal correlations with respect to the reaction
plane for Pb--Pb collisions at TeV recorded in 2010 with
ALICE at the LHC. The results are compared with measurements at RHIC energies
and against currently available model predictions for LHC. Systematic studies
of possible background effects including comparison with conventional
(parity-even) correlations simulated with Monte Carlo event generators of
heavy--ion collisions are also presented.Comment: Published in the proceedings of "Quark Matter 2011", Annecy-Franc
Dynamic IMF production in at intermediate energies
The azimuthal correlations and polar-angle distributions of intermediate-mass fragments (IMFs) produced in Mg+Al at 45 an 95 AMeV were studied. Measurements of -particles and IMFs with emmitted in the mid-rapidity region for mid-central events were compared to IQMD results and results from a static-source model. A maximum in the azimuthal-correlation function at 180\degree\/ can not be described by independently emmitted particles. Momentum conservation of a small source as well as target-projectile correlations from IQMD show the same azimuthal correlations as the experimental data. The polar-angle distributions in the experimental data show a target-projectile seperation, thus giving evidence of dynamic IMF production.\\ {\it Keywords:} dynamic multifragmentation, IMF, IQMD, azimuthal correlations
Quark-Gluon Plasma at RHIC and the LHC: Perfect Fluid too Perfect?
Relativistic heavy ion collisions have reached energies that enable the
creation of a novel state of matter termed the quark-gluon plasma. Many
observables point to a picture of the medium as rapidly equilibrating and
expanding as a nearly inviscid fluid. In this article, we explore the evolution
of experimental flow observables as a function of collision energy and attempt
to reconcile the observed similarities across a broad energy regime in terms of
the initial conditions and viscous hydrodynamics. If the initial spatial
anisotropies are very similar for all collision energies from 39 GeV to 2.76
TeV, we find that viscous hydrodynamics might be consistent with the level of
agreement for v2 of unidentified hadrons as a function of pT . However, we
predict a strong collision energy dependence for the proton v2(pT). The results
presented in this paper highlight the need for more systematic studies and a
re-evaluation of previously stated sensitivities to the early time dynamics and
properties of the medium.Comment: 11 pages, 9 figures, submitted to the New Journal of Physics focus
issue "Strongly Correlated Quantum Fluids: From Ultracold Quantum Gases to
QCD Plasmas
Elliptic Flow: A Brief Review
One of the fundamental questions in the field of subatomic physics is what
happens to matter at extreme densities and temperatures as may have existed in
the first microseconds after the Big Bang and exists, perhaps, in the core of
dense neutron stars. The aim of heavy-ion physics is to collide nuclei at very
high energies and thereby create such a state of matter in the laboratory. The
experimental program started in the 1990's with collisions made available at
the Brookhaven Alternating Gradient Synchrotron (AGS), the CERN Super Proton
Synchrotron (SPS) and continued at the Brookhaven Relativistic Heavy-Ion
Collider (RHIC) with maximum center of mass energies of 4.75, 17.2 and 200 GeV
respectively. Collisions of heavy-ions at the unprecedented energy of 2.76 TeV
have recently become available at the LHC collider at CERN. In this review I
will give a brief introduction to the physics of ultra-relativistic heavy-ion
collisions and discuss the current status of elliptic flow measurements.Comment: version accepted by NJ
Directed and Elliptic Flow at RHIC
We present the directed flow measurement () from Au+Au collisions at
\sqrtsNN = 62 GeV. Over the pseudorapidity range we have studied, which
covers from -1.2 to 1.2 and , the magnitude of
for charged particles is found to increase monotonously with pseudorapidity for
all centralities. No `` wiggle'', as predicted by various theoretical
models, is observed at midrapidity. Elliptic flow () from moderate high
particles () at \sqrtsNN = 200 GeV is presented as a
function of impact parameter. It is found that models that are based on {\it
jet quenching} alone appear to underpredict at moderate high , while
the model that incorporates both, recombination and fragmentation, describes
the data better.Comment: 6 pages, 4 figures. Proceeding for Hot Quark 04 conference Changes in
the revision are mostly English fixes. v1 versus eta plot is flipped over to
follow the conventio
Anisotropic Flow from RHIC to the LHC
Anisotropic flow is recognized as one of the main observables providing
information on the early stage of a heavy-ion collision. At RHIC the large
observed anisotropic flow and its successful description by ideal hydrodynamics
is considered evidence for an early onset of thermalization and almost ideal
fluid properties of the produced strongly coupled Quark Gluon Plasma. This
write-up discusses some key RHIC anisotropic flow measurements and for
anisotropic flow at the LHC some predictions.Comment: 4 pages, 6 figures, hotquarks 200
Flow at the SPS and RHIC as a Quark Gluon Plasma Signature
Radial and elliptic flow in non-central heavy ion collisions can constrain
the effective Equation of State(EoS) of the excited nuclear matter. To this
end, a model combining relativistic hydrodynamics and a hadronic transport
code(RQMD [17]) is developed. For an EoS with a first order phase transition,
the model reproduces both the radial and elliptic flow data at the SPS. With
the EoS fixed from SPS data, we quantify predictions at RHIC where the Quark
Gluon Plasma(QGP) pressure is expected to drive additional radial and elliptic
flow. Currently, the strong elliptic flow observed in the first RHIC
measurements does not conclusively signal this nascent QGP pressure. Additional
measurements are suggested to pin down the EoS.Comment: 4 pages, 4 figures. Revised. Included discussed of v_2 (p_t) vs. b
and comparison to STAR dat
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