302 research outputs found

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

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    Using the (2+1)-dimensional ultrarelativistic viscous hydrodynamics+hadron cascade, VISHNU, hybrid model, we study the pTp_{\rm T}-spectra and elliptic flow of Λ\Lambda, Ξ\Xi, and Ω\Omega in Au+Au collisions at sNN\sqrt{s_{NN}}=200 GeV and in Pb+Pb collisions at sNN\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 v2v_{2} among π\pi, KK, pp, Λ\Lambda, Ξ\Xi, and Ω\Omega are further investigated and discussed at the two collision systems. We find, at both RHIC and LHC, the v2v_{2} mass ordering among π\pi, KK, pp, and Ω\Omega are fairly reproduced within the VISHNU hybrid model, and more improvements are needed to implement for well describing the v2v_{2} mass ordering among pp, Λ\Lambda, and Ξ\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

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    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, IAAI_{\rm AA} and ICPI_{\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, xEpTγpTh±pTγ2x_{\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

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    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, Ξ\Xi and Ω\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

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    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 SCv(m,n)SC^{v}(m, n), the normalized symmetric cumulants NSC(m,n)NSC(m, n), and the Pearson correlation coefficients C(vm2,vn2)C(v_{m}^{2}, v_{n}^{2}) in 2.76A TeV Pb--Pb collisions. We find SCv(m,n)SC^{v}(m, n) is sensitive to both initial conditions and the specific shear viscosity η/s\eta/s. A comparison with the recent ALICE data show that our hydrodynamic calculations can qualitatively describe the data of SCv(3,2)SC^{v}(3, 2) and SCv(4,2)SC^{v}(4, 2) for various initial conditions, which demonstrate that v2v_2, v4v_4 are correlated and v2v_2, v3v_3 are anti-correlated. Meanwhile, the predicted symmetric cumulants SCv(5,2)SC^{v}(5, 2), SCv(5,3)SC^{v}(5, 3), and SCv(4,3)SC^{v}(4, 3) reveal that v2v_2 and v5v_5, v3v_3 and v5v_5 are correlated, v3v_3 and v4v_4 are anti-correlated in most centrality classes. We also find NSCv(3,2)NSC^{v}(3, 2) and C(v32,v22)C(v_{3}^{2}, v_{2}^{2}), which are insensitive to η/s\eta/s, are mainly determined by corresponding NSCε(3,2)NSC^{\varepsilon}(3, 2) and C(ε32,ε22)C(\varepsilon_{3}^{2}, \varepsilon_{2}^{2}) correlators from the initial state. In contrast, other NSCv(m,n)NSC^{v}(m, n) and C(vm2,vn2)C(v_{m}^{2}, v_{n}^{2}) correlators are influenced by both initial conditions and η/s\eta/s, which illustrates the non-linear mode couplings in higher flow harmonics with n4n \geq 4.Comment: 10 pages, 7 figure

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

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    Using the Ultra-relativistic Quantum Molecular Dynamics ({\tt UrQMD}) model, we investigate the azimuthal correlations in p--Pb collisions at sNN=5.02\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 v2(pT)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

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    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 SCv(m,n)SC^{v}(m, n) and the normalized symmetric cumulants NSCv(m,n)NSC^{v}(m, n), and found v2v_{2} and v4v_{4}, v2v_{2} and v5v_{5}, v3v_{3} and v5v_{5} are correlated, v2v_{2} and v3v_{3}, v3v_{3} and v4v_{4} are anti-correlated. We also found NSCv(3,2)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

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    Using the VISHNU hybrid model, we calculate the multiplicity, spectra, and elliptic flow of Λ\Lambda, Ξ\Xi and Ω\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 π\pi, K, p, Λ\Lambda, Ξ\Xi and Ω\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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