302 research outputs found

### Spectra and elliptic flow of (multi-)strange hadrons at RHIC and LHC within viscous hydrodynamics+hadron cascade hybrid model

Using the (2+1)-dimensional ultrarelativistic viscous hydrodynamics+hadron
cascade, VISHNU, hybrid model, we study the $p_{\rm T}$-spectra and elliptic
flow of $\Lambda$, $\Xi$, and $\Omega$ in Au+Au collisions at
$\sqrt{s_{NN}}$=200 GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV.
Comparing our model results with the data measurements, we find that the VISHNU
model gives general descriptions of the measurements of these strange and
multi-strange hadrons at several centrality classes at RHIC and LHC. Mass
ordering of elliptic flow $v_{2}$ among $\pi$, $K$, $p$, $\Lambda$, $\Xi$, and
$\Omega$ are further investigated and discussed at the two collision systems.
We find, at both RHIC and LHC, the $v_{2}$ mass ordering among $\pi$, $K$, $p$,
and $\Omega$ are fairly reproduced within the VISHNU hybrid model, and more
improvements are needed to implement for well describing the $v_{2}$ mass
ordering among $p$, $\Lambda$, and $\Xi$.Comment: revise the draft according to the reviewers` comments, 7 pages, 5
figure

### Two-particle correlations in pp and Pb-Pb collisions with ALICE

The measurement of azimuthal correlations between two particles is a powerful
tool to investigate the properties of strongly-interacting nuclear matter
created in ultra-relativistic heavy-ion collisions. We present measurements of
di-hadron correlations in azimuth angle and pseudorapidity in Pb-Pb collisions
at \sqrt{s_{\rm NN}} = 2.76 \tev and photon-hadron correlations in pp
collisions at \sqrt{s} = 7 \tev with the ALICE detector, respectively. In
di-hadron correlations, the near-side jet shape in the short-range correlation
region is quantitatively analyzed at \ptt < 8 \gmom, and the modification of
jet-particle yield, $I_{\rm AA}$ and $I_{\rm CP}$, is measured at 8 < \ptt <
15 \gmom. In photon-hadron correlations, isolated leading photon and
associated hadrons in its opposite azimuthal direction correlations are used to
estimate the jet fragmentation function via the imbalance parameter, $x_{\rm E}
\equiv -\frac{\vec{p}_{\rm T}^{\gamma}\cdot\vec{p}_{\rm T}^{\rm
h^{\pm}}}{|\vec{p}_{\rm T}^{\gamma}|^{2}}$.Comment: 10 pages, 14 figures, Proceedings for Hadron Nuclear Physics
2013-HNP2013, 18-22 July 2013, Zhangjiajie, Chin

### Chemical and thermal freeze-out of identified hadrons at the LHC

This proceeding briefly summarizes our recent VISHNU hybrid model
investigations on the chemical and thermal freeze-out of various hadrons
species in 2.76 A TeV Pb+Pb collisions. Detailed analysis on the evolution of
particle yields and the last elastic collisions distributions during the
hadronic evolution reveals that the two multi-strange hadrons, $\Xi$ and
$\Omega$, experience early chemical and thermal freeze-out when compared with
other hadron species.Comment: 4 pages, 3 figures, SQM2015 proceedin

### Correlations of flow harmonics in 2.76A TeV Pb--Pb collisions

Using the event-by-event viscous hydrodynamics VISH2+1 with MC-Glauber,
MC-KLN, and AMPT initial conditions, we investigate the correlations of flow
harmonics, including the symmetric cumulants $SC^{v}(m, n)$, the normalized
symmetric cumulants $NSC(m, n)$, and the Pearson correlation coefficients
$C(v_{m}^{2}, v_{n}^{2})$ in 2.76A TeV Pb--Pb collisions. We find $SC^{v}(m,
n)$ is sensitive to both initial conditions and the specific shear viscosity
$\eta/s$. A comparison with the recent ALICE data show that our hydrodynamic
calculations can qualitatively describe the data of $SC^{v}(3, 2)$ and
$SC^{v}(4, 2)$ for various initial conditions, which demonstrate that $v_2$,
$v_4$ are correlated and $v_2$, $v_3$ are anti-correlated. Meanwhile, the
predicted symmetric cumulants $SC^{v}(5, 2)$, $SC^{v}(5, 3)$, and $SC^{v}(4,
3)$ reveal that $v_2$ and $v_5$, $v_3$ and $v_5$ are correlated, $v_3$ and
$v_4$ are anti-correlated in most centrality classes. We also find $NSC^{v}(3,
2)$ and $C(v_{3}^{2}, v_{2}^{2})$, which are insensitive to $\eta/s$, are
mainly determined by corresponding $NSC^{\varepsilon}(3, 2)$ and
$C(\varepsilon_{3}^{2}, \varepsilon_{2}^{2})$ correlators from the initial
state. In contrast, other $NSC^{v}(m, n)$ and $C(v_{m}^{2}, v_{n}^{2})$
correlators are influenced by both initial conditions and $\eta/s$, which
illustrates the non-linear mode couplings in higher flow harmonics with $n \geq
4$.Comment: 10 pages, 7 figure

### Is hadronic flow produced in p--Pb collisions at the Large Hadron Collider?

Using the Ultra-relativistic Quantum Molecular Dynamics ({\tt UrQMD}) model,
we investigate the azimuthal correlations in p--Pb collisions at
$\sqrt{s_{_{\rm NN}}}=5.02$ TeV. It is shown that the simulated hadronic p--Pb
system can not generate the collective flow signatures, but mainly behaves as a
non-flow dominant system. However, the characteristic $v_{2}(p_{\rm T})$
mass-ordering of pions, kaons and protons is observed in {\tt UrQMD}
simulations, which is the consequence of hadronic interactions and not
necessarily associated with strong fluid-like expansions.Comment: 4 pages, 4 figures, proceedings for the 12th International Conference
on Nucleus-Nucleus Collisions (21-26 June 2015, Catania

### Investigating the correlations of flow harmonics in 2.76A TeV Pb--Pb collisions

This proceeding briefly summarizes our recent investigations on the
correlations of flow harmonics in 2.76A TeV Pb--Pb collisions with viscous
hydrodynamics {\tt VISH2+1}. We calculated both the symmetric cumulants
$SC^{v}(m, n)$ and the normalized symmetric cumulants $NSC^{v}(m, n)$, and
found $v_{2}$ and $v_{4}$, $v_{2}$ and $v_{5}$, $v_{3}$ and $v_{5}$ are
correlated, $v_{2}$ and $v_{3}$, $v_{3}$ and $v_{4}$ are anti-correlated. We
also found $NSC^{v}(3, 2)$ are insensitive to the QGP viscosity, which are
mainly determined by the initial conditions.Comment: SQM2016 proceeding, 4pages, 2 figure

### A hybrid model approach for strange and multi-strange hadrons in 2.76 A TeV Pb+Pb collisions

Using the VISHNU hybrid model, we calculate the multiplicity, spectra, and
elliptic flow of $\Lambda$, $\Xi$ and $\Omega$ in 2.76 A TeV Pb+Pb collisions.
Comparisons between our calculations and the ALICE measurements show that the
model generally describes the soft hadron data of these strange and
multi-strange hadrons at several centrality bins. Mass ordering of elliptic
flow among $\pi$, K, p, $\Lambda$, $\Xi$ and $\Omega$ has also been studied and
discussed. With a nice description of the particle yields, we explore chemical
and thermal freeze-out of various hadrons species at the LHC within the
framework of the VISHNU hybrid model.Comment: version 2: with several references added, published in PR

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