Narrow Results

In high energy heavy ion collisions of RHIC and LHC, a strongly interacting quark gluon plasma (sQGP) is created. This medium undergoes a hydrodynamic evolution, before it freezes out to form a hadronic matter. The initial state of the sQGP is determined by the initial distribution of the participating nucleons and their interactions. Due to the finite number of nucleons, the initial distribution fluctuates on an event-by-event basis. The transverse plane anisotropy of the initial state can be translated into a series of anisotropy coefficients or eccentricities: second, third, fourth-order anisotropy etc. These anisotropies then evolve in time, and result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we investigate the time evolution of the anisotropies. With a numerical hydrodynamic code, we analyze how the speed of sound and viscosity influence this evolution.

In this paper, we present systematic measurements of azimuthal anisotropy for strange hadrons ($K_s^0$, $\varphi$ and $\mathrm{\Lambda }$) and multi-strange hadrons ($\mathrm{\Xi }$ and $\mathrm{\Omega }$) at mid-rapidity ($\left|y\right|<1.0$) in U$+$U collisions at $\sqrt{s_{NN}}=193$ GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). Flow coefficients ($v_2$, $v_3$ and $v_4$) are presented as a function of transverse momentum ($p_T$) for minimum bias and three different centrality intervals. The $\eta$ sub-event plane method is used to obtain the results. These measurements are compared with the published results from Au$+$Au collisions at $\sqrt{s_{NN}}=200$ GeV. Number of Constituent Quark (NCQ) scaling of the measured flow coefficients in U$+$U collisions is discussed. We also present the ratio of $v_n$ scaled by the participant eccentricity (${𝜀}_n\{2\}$) to explore system size dependence and collectivity in U$+$U collisions. The measured flow coefficients are compared with hydrodynamic and transport model calculations.

We present a review of published experimental measurements on anisotropic flow in heavy-ion collisions. Flow coefficients $v_n$ are presented for charged and identified hadrons at various beam energies ranging from $\sqrt{s_{\mathrm{\text{NN}}}}=7.7$GeV to 200GeV at the Relativistic Heavy Ion Collider (RHIC) and $\sqrt{s_{\mathrm{\text{NN}}}}=2760$GeV at the Large Hadron Collider (LHC). We present $v_1$ and its slope $d{v}_1∕dy$ and discuss possible first-order Quantum chromodynamics (QCD) phase transition. $v_1$ of particles containing heavy quarks (Charm quarks) is also discussed to illustrate the effect of the magnetic field produced in relativistic heavy-ion collisions. We also present flow harmonics ($v_2$, $v_3$ and $v_4$) for inclusive charged and identified hadrons. We compare the charged particle $v_n$ coefficients with hydrodynamics to study and constrain initial conditions in the transport models. The results of identified particle $v_2$ from ideal and viscous hydrodynamics are discussed to understand the dynamics and mechanism of particle production in high-energy nuclear collisions.

In high energy heavy ion collisions of RHIC and LHC, a strongly interacting quark gluon plasma (sQGP) is created. This medium undergoes a hydrodynamic evolution, before it freezes out to form a hadronic matter. The initial state of the sQGP is determined by the initial distribution of the participating nucleons and their interactions. Due to the finite number of nucleons, the initial distribution fluctuates on an event-by-event basis. The transverse plane anisotropy of the initial state can be translated into a series of anisotropy coefficients or eccentricities: second, third, fourth-order anisotropy etc. These anisotropies then evolve in time, and result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we investigate the time evolution of the anisotropies. With a numerical hydrodynamic code, we analyze how the speed of sound and viscosity influence this evolution.