Navegando por Autor "Qian, Weiliang"
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Item Deformed even-even nuclei in a quark-meson coupling model with tensor coupling.(2013) Xu, R. L.; Wu, Chen; Qian, Weiliang; Ren, Z. Z.; Liu, J.In this work, a new quark-meson coupling model is employed to study the ground-state properties of axially deformed even-even nuclei. Two essential ingredients, namely, density dependence of quark mass and tensor coupling, play important roles in our approach. In particular, it is the first time that the deformed quark-meson coupling calculation with tensor coupling is applied to study the properties of finite nuclei. The present work involves a systematical study of nuclei ranging from Z = 50 to Z = 82. The ground-state binding energies, quadrupole deformations, shape coexistence, two-neutron separation energies and the root-mean-square charge radii are calculated and compared with the experimental data. It is shown that the ground-state properties of the deformed nuclei are reasonably well reproduced by a model based on the sub-hadronic degrees of freedom.Item Effective nucleon mass and thermodynamics in the quark-meson coupling model.(2012) Wu, Chen; Ma, Yu-Gang; Kumar, Sanjeev; Cao, Xi-Guang; Qian, WeiliangIn this work, we study the quark energy spectrum in an MIT bag using the quark-meson coupling model. In particular, thermal distribution functions of quarks at finite temperature are explicitly incorporated into the calculations. It is found that when temperature is less than 50 MeV, the probability for a quark to occupy an exciting state is very rare and negligible, therefore the corresponding contributions to the thermodynamic potential undermean-field theory are strongly suppressed. In this context, if one calculates other physical quantities derived from thermodynamic potential, effects due to quark distribution functions are also likely to be unimportant.Item Further results on peripheral-tube model for ridge correlation.(2013) Hama, Yogiro; Andrade, Rone Peterson Galvao de; Grassi, Frederique; Noronha, Jorge; Qian, WeiliangPeripheral one-tube model has shown to be a nice tool for dynamically understanding several aspects of ridge structures in long-range two-particle correlations, observed experimentally and obtained also in our model calculations using NexSPheRIO code. Here, we study an extension of the model, to initial configurations with several peripheral tubes distributed randomly in azimuth. We show that the two-particle correlation is almost independent of the number of tubes, although the flow distribution becomes indeed strongly event dependent. In our picture, the ridge structures are causally connected not only in the longitudinal direction but also in azimuth.Item Hydrodynamics : fluctuating initial conditions and two-particle correlations.(2011) Andrade, Rone Peterson Galvao de; Grassi, Frederique; Hama, Yogiro; Qian, WeiliangEvent-by-event hydrodynamics (or hydrodynamics with fluctuating initial conditions) has been developed in the past few years. Here we discuss how it may help to understand the various structures observed in two-particle correlations.Item NeXSPheRIO results on elliptic flow and directed flow for Au+Au and Cu+Cu collisions at RHIC.(2010) Andrade, Rone Peterson Galvao de; Reis, A. dos; Grassi, Frederique; Hama, Yogiro; Kodama, T.; Ollitrault, J. Y.; Qian, WeiliangHydrodynamics has been rather successful at describing results obtained in relativistic nuclear collisions at RHIC. Here we show results obtained with NeXSPheRIO on Au+Au collisions and the less studied Cu+Cu collisions. We study elliptic flow and its connection with eccentricity suggested by PHOBOS, as well as present elliptic flow fluctuations. We also show results for directed flow and compare with PHOBOS and STAR data.Item Origin of trigger-angle dependence of di-hadron correlations.(2013) Qian, Weiliang; Andrade, Rone Peterson Galvao de; Gardim, Fernando; Grassi, Frederique; Hama, YogiroThe STAR Collaboration reported measurements of di-hadron azimuthal correlations in medium-central Au+Au collisions at 200A GeV, where the data are presented as a function of the trigger particle’s azimuthal angle relative to the event plane φs . In particular, it is observed that the away-side correlation evolves from a singleto a double-peak structure with increasing φs . In this work, we present the calculated correlations as functions of both φs and the particle transverse momentum pT , using the hydrodynamic code NeXSPheRIO. The results are found to be in reasonable agreement with the STAR data. We further argue that the above φs dependence of the correlation structure can be understood in terms of the one-tube model, as due to an interplay between the background elliptic flow caused by the initial state global geometry and the flow produced by fluctuations.Item Quark deconfinement phase transition in nuclear matter for improved quark mass density-dependent model.(2012) Wu, Chen; Qian, Weiliang; Ma, Yu-Gang; Zhang, Guo-Qiang; Kumar, SanjeevThe improved quark mass density-dependent (IQMDD) model, which has been successfully used to describe the properties of both infinite nuclear matter and finite nuclei, is applied to investigate the properties of quark deconfinement phase transition. By using the finite temperature quantum field theory, we calculate the finite temperature effective potential and extend the IQMDD model to finite temperature and finite nuclear matter density. The critical temperature and the critical density of nuclear matter are given and the QCD phase diagram is addressed. It is shown that this model can not only describe the saturation properties of nuclear matter, but also explain the quark deconfinement phase transition successfully.Item Temporal evolution of tubular initial conditions and their influence on two-particle correlations in relativistic nuclear collisions.(2012) Andrade, Rone Peterson Galvao de; Grassi, Frederique; Hama, Yogiro; Qian, WeiliangRelativistic nuclear collisions data on two-particle correlations exhibit structures as function of relative azimuthal angle and rapidity. A unified description of these near-side and away-side structures is proposed for low to moderate transverse momentum. It is based on the combined effect of tubular initial conditions and hydrodynamical expansion. Contrary to expectations, the hydrodynamics solution shows that the high-energy density tubes (leftover from the initial particle interactions) give rise to particle emission in two directions and this is what leads to the various structures. This description is sensitive to some of the initial tube parameters and may provide a probe of the strong interaction. This explanation is compared with an alternative one where some triangularity in the initial conditions is assumed. A possible experimental test is suggested.Item The ridge as a shadowing effect in hydrodynamics.(2011) Andrade, Rone Peterson Galvao de; Grassi, Frederique; Hama, Yogiro; Qian, WeiliangThe aim of this work is to clarify the origin of the inplane/outofplane effect, in the twoparticle correlation function, computed with the NexSPheRIO code, in Au + Au collisions at 200 AGeV. We show that such an effect can be understood in terms of the shadowing effect caused by a peripheral highenergy density tube.