Session FC: Flow II

Identified particle $v_{1}$ and $v_{2}$ in $\sqrt{s_{NN}}$ = 3 GeV Au+Au collisions at STAR

Directed flow ($v_{1}$) and elliptic flow ($v_{2}$) are important observables in the relativistic heavy-ion collisions, as they are established during the early stage of the system evolution, which can allow us to access the collective properties of the expanding system. This is an important part of our program for studying the QCD phase structure at RHIC. In this talk, we will present the centrality dependence of identified particle ($\pi^{\pm}$, $K^{\pm}$, p) $v_{1}$ and $v_{2}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV with the fixed-target mode (beam energy of 3.85 GeV/u) at STAR. The transverse momentum ($p_{T}$) and rapidity (y) dependence of identified particle $v_{1}$ and $v_{2}$ will be discussed. We will also discuss the number of constituent quark (NCQ) scaling in $v_{2}$ and energy dependence of $v_{1}$ and $v_{2}$, these results will be compared to that from STAR BES-I data. In addition, model calculations of $v_{1}$ and $v_{2}$ for those identified hadrons will also be discussed.   

\(\phi\) meson \(v_{1}\), \(v_{2}\) in Au+Au collisions at \(\sqrt{s_{NN}} = \) 3 GeV, 7.2 GeV from STAR

The \(\phi\) meson is composed of strange quarks (\(s\overline s\)), and has a small cross section with hadrons which reduces the influence of rescattering in the later stage of heavy-ion collisions. Thus the \(\phi\) meson directed flow (\(v_{1}\)) and elliptic flow (\(v_{2}\)) are sensitive to the early stages of the collisions and are important observables for the study of quark-gluon plasma (QGP) phase diagram at RHIC. In this talk, we will present measurements of the \(\phi\) meson \(v_{1}\), \(v_{2}\) in Au+Au collisions from the STAR fixed-target program (FXT). The \(\phi\) meson is reconstructed through the channel \(\phi\rightarrow K^{+}+ K^{-}\). We will compare our new results with STAR Beam Energy Scan I (BES-I) results.   

Including a 4-Dimensional Equation of State in Smoothed Particle Hydrodynamics

The Beam Energy Scan program at RHIC is currently searching for a QCD thermodynamic critical point that is conjectured to exist at a large value of baryonic chemical potential, $\mu_B$. It is also the case, that at finite baryon densities, one necessarily has finite densities of both strangeness and electric charge, which are both good conserved quantities throughout the hydrodynamic evolution. These come with their own respective chemical potentials, $\mu_S$ and $\mu_Q$, making it necessary to incorporate these quantities into the hydrodynamics by both including a 4-D equation of state $\{T,\mu_B,\mu_S,\mu_Q\}$, and charge current and diffusion evolution for all four quantities. In this work, we focus on the application and derivation of the charge current evolution equations in the context of Smoothed Particle Hydrodynamics.   

$v_{n}$ measurement in Au+Au collisions at $\sqrt{s_{NN}} =$ 27 GeV with the Event Plane Detector from STAR

The measurement of pseudorapidity ($\eta$) dependence of $v_{n}$ at lower collision energies can provide unique constraints on the three-dimensional initial conditions, baryon transport, shear viscosity over entropy density as well as its dependence on temperature and baryon chemical potential. The combination of the Event Plane Detector (EPD, $2.1<|\eta|<5.1$) installed in the year 2018, STAR time projection chamber (TPC, $|\eta|<1$) and high statistics Beam Energy Scan phase-II data enables us to perform precise measurements of $v_{n}(\eta)$. In this presentation, we will show the directed flow ($v_{1}(\eta)$) and elliptic flow ($v_{2}(\eta)$) of charged hadrons measured over ten units of pseudorapidity using $\sqrt{s_{NN}} =$ 27 GeV Au+Au data taken in 2018 and the comparisons to hydrodynamic model predictions. We observed a sign change of $v_{1}(\eta)$ at $\eta=Y_{beam}$ and longitudinal scaling of $v_1$ with $|\eta|-Y_{beam}$ when compared with earlier measurements from the PHOBOS collaboration. We will also present the transverse momentum ($p_{T}$) dependence of $v_{1}$ at midrapidity.   

Study of Longitudinal Event-plane Decorrelation in Heavy-ion Collisions with a Multiphase Transport Model

Measurements of pseudorapidity ($\eta$) dependence of local event-plane (EP) correlations provide novel inputs to the initial conditions in heavy-ion collisions. A factorization ratio of elliptic flow ($v_2$), $r_2(\eta) = \langle v_2(-\eta) \cos[2(\Psi_{\rm m,-\eta}-\Psi_{\rm f})]\rangle / \langle v_2(\eta) \cos[2(\Psi_{\rm m,\eta}-\Psi_{\rm f})]\rangle$, has been extensively used to quantify the decorrelation between two EPs at midrapidities ($\Psi_{{\rm m},\pm\eta}$) using a forward EP ($\Psi_{\rm f}$) as a reference. However, nonflow effects could cause features in $r_2$ similar to decorrelation. In this study, we shall employ a multiphase transport model (AMPT) to evaluate the sensitivity of several methods to both decorrelation and nonflow. Differential measurements of $r_2(\eta)$ and its slope, $F_2$, as well as their modified forms indicated possible nonflow effect contribution. We propose an alternative observable, $T_2 = \langle\sin(2(\Psi_{f} -\Psi_{m,1})) \sin(2(\Psi_{b} -\Psi_{m,2}))\rangle$, which has different sensitivity to dynamics of decorrelation from twist of initial participant matter and/or nonflow effect. We employ event-shape selection analysis technique to investigate features in $F_2$ and $T_2$, and discuss their physics implications.   

Measurement of initial-state fluctuations using principal-components of elliptic and triangular flow in $\sqrt{s_{NN}}$ = 3.0 GeV Au+Au collisions at the STAR detector

Initial-state fluctuations could contribute to the factorization breaking in two-particle azimuthal correlations $V_{n\Delta}(p^{a},p^{b})$ at high transverse momentum $p_{T}$. Principal-component analysis (PCA) provides a set of novel experimental observables ($V_{n}^{1}(p_{T})$,$V_{n}^{2}(p_{T})$,...) which directly quantifies the magnitude of the factorization breaking caused by the initial-state fluctuations to high accuracy, by expanding the complex flow coefficient using the orthogonal principal components built from a symmetric and semidefinite covariance data matrices. Measuring of initial-state fluctuations from STAR BES-II collision energies with relatively high baryon chemical potential could provide further constraints for theoretical models on Quark-Gluon Plasma (QGP) properties. In this analysis, we present the measurement of the first two leading components for n=2,3 extracted from $\sqrt{s_{NN}}$ = 3.0 GeV Au+Au collisions at STAR.   

PHENIX measurements of elliptic flow of prompt hadrons and inclusive muons atrapidity in 200 GeV Au$+$Au collisions

Near perfect fluid behavior is a hallmark signature of the quark gluon plasma(QGP), however, how this behavior emerges is still not fully understood. Thus,of many different types of particles over a wide rapidity range areto understand this phenomenon. PHENIX has unique capabilities for measuringat forward rapidity using the forward silicon vertex detector (FVTX) and muon. The flow of heavy flavor particles can be measured via their decayusing PHENIX's forward rapidity instrumentation. In addition, the FVTX allowsthe separation of decay muons from charm and beauty particles respectively. We willthe latest analysis status for the elliptic flow of prompt hadrons and inclusiveat forward rapidity as progress towards the measurement of the flow of charmbeauty particles at forward rapidity.   

Elliptic flow of prompt $D^0$ meson via multi-particle correlations in PbPb collisions at 5.02 TeV

Measurements of the flow harmonic $v_2$ of prompt $D^0$ and $\bar{D^0}$ mesons are presented via the hadronic decay channels $D^0$ $\rightarrow$ $K^-\pi^{+}$ and $\bar{D^0}$ $\rightarrow$ $K^+\pi^{-}$ PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV per nucleon pair, using high statistics data sample collected by the CMS detector during the 2018 LHC Run. A four-particle cumulant technique is employed to measure $D^0$ $v_2$ for the first time in PbPb collisions. These results strength the evidence of collective phenonmena in large hadronic collision systems. Furthermore, the specific variation of the $v_2{\{4\}}/v_2{\{2\}}$ ratios with respect to transverse momentum and centrality, which are compared to some theoretical predictions, is also studied in the context of heavy flavor.   

PHENIX Measurement of J/$\psi$ Elliptic Flow in 200 GeV Au+Au Collisions at Forward Rapidity

The Quark Gluon Plasma (QGP) produced in relativistic heavy ion collisions exhibits a nearly perfect fluid behavior, which manifests itself in strong azimuthal correlations between the produced particles. This behavior is seen for both light and heavy-flavor particles, but the detailed interactions of the heavy quarks in the medium are still under investigation. Quarkonia may serve as a special probe, as they are subject to several competing effects that involve interactions of both the bound state and the individual heavy quarks with the QGP. PHENIX has unique coverage at forward rapidity and a large data set of Au+Au collisions at 200 GeV collected in 2014 that will allow for a statistically improved measurement of J/$\psi$ elliptic flow. The status of the J/$\psi$ flow analysis will be presented.