We report on the first evidence for a non-zero rapidity-odd directed flow ($v_{1}$) for $D^{0}$ and $\overline{D^{0}}$ mesons in 10-80\% centrality Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200~GeV measured with the STAR detector at RHIC. The slope of the $v_1$ rapidity dependence ($dv_{1}/dy$) averaged over $D^{0}$ and $\overline{D^{0}}$ mesons is -0.081 $\pm$ 0.021 $\pm$ 0.017, while that of charged kaons is -0.0030 $\pm$ 0.0001 $\pm$ 0.0002, suggesting significantly larger slope for the $D^{0}$ mesons. Models indicate that the large $dv_{1}/dy$ of $D^{0}$ mesons is sensitive to the initially tilted source. We also present a new measurement of the $D^{0}$ meson elliptic flow ($v_2$) as a function of transverse momentum ($p_{T}$) in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200~GeV with an improved precision with respect to the previously published results.The $D^{0}$ $v_{2}$ results are compared to those of light-flavor hadrons to test the number-of-constituent-quark (NCQ) scaling. Both the $v_{1}$ and $v_{2}$ results are compared to recent hydrodynamic and transport model calculations.
An improved Tsallis statistics is implemented in a multisource thermal model to describe systematically pseudorapidity spectra of charged particles produced in relativistic nucleon-nucleon ($pp$ or $p\overline{p}$) collisions at various collision energies and in relativistic nucleus-nucleus ($AA$) collisions at different energies with different centralities. The results with Tsallis statistics using the two-cylindrical multisource thermal model are in good agreement with the experimental data measured at RHIC and LHC energies. It is found that the rapidity shifts of longitudinal sources increa…
We report results of $v_1(y)$ and $dv_1/dy$ near mid-rapidity for $π^{\pm}$, $K^{\pm}$, $K_s^0$, $p$, $\overline{p}$, $Λ$, $\overlineΛ$ and $ϕ$ from Beam Energy Scan Au+Au collisions at $\sqrt{s_{NN}} = $ 7.7 - 200 GeV using the STAR detector at RHIC. The $dv_{1}/dy$ of $π^{\pm}$, $K^{\pm}$ and $K_s^0$ mesons remains negative over all beam energies. The $dv_1/dy$ of $p$ and $Λ$ baryons shows a sign change around 10 - 15 GeV, while net baryons (net p and net $Λ$) indicate a double sign change. The $dv_1/dy$ of $\overline{p}$, $\overlineΛ$ and $ϕ$ show a similar trend for $\sqrt{s_{NN}}>$ 14.5 G…
Charm quarks, owing to their large mass, are produced predominantly in the initial hard scatterings in heavy-ion collisions, and therefore can be a valuable tool for studying the early time dynamics of these collisions. The rapidity-odd directed flow at mid-rapidity in heavy-ion collisions originates from a tilt in the reaction plane of the thermalized medium caused by the asymmetry between the number of participants from projectile and target nuclei as a function of rapidity. Recently, it has been predicted that the slope of the directed flow at mid-rapidity for $D^0$ mesons, arising from the…
We study the directed flow of identified particles in Au+Au collisions at $\sqrt{s_\text{NN}}=7.7$ to 62.4 GeV. The Glauber model is extended to include both a tilted deformation of the QGP fireball with respect to the longitudinal direction and a non-zero longitudinal flow velocity gradient in the initial state. By combining this improved initial condition with a (3+1)-dimensional viscous hydrodynamic model calculation, we obtain a satisfactory description of the transverse momentum spectra and the rapidity dependent directed flow coefficient of different hadron species. Our calculation indic…
Analysis of directed flow ($v_1$) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of collision energies $\sqrt{s_{NN}}$ = 2.7--39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS with deconfinement transitions: a first-order phase transition and a smooth crossover transition. The crossover EoS is unambiguously preferable for the description of the most part of experimental data in this energy range. The directed flow indicates that the crossover deconfinement transition…
We present the STAR measurements of directed flow, v1, for π{\pm}, K{\pm}, protons and antiprotons, as well as for all detected charged particles in Au + Au collisions at {\surd}sNN = 7.7, 11.5 and 39 GeV as a function of transverse momentum, rapidity and centrality. Results are compared to the predictions from transport models.
Directed flow, v1, of charged hardons has been measured in Au-Au collisions at RHIC for center-of-mass energies sqrt(sNN) = 19.6, 130, 62.4, and 200 GeV using the PHOBOS detector. The large acceptance of PHOBOS for charged particles allows measurements over the full range of pseudorapidity |eta| <5.4. The results for a symmetric subevent method are shown at all four energies. Comparison is made to a mixed harmonic method for the highest energy, and compared to similar results from the STAR collaboration.
We compute the $Λ$ and $\overlineΛ$ global polarizations in semi-central heavy-ion collisions using the core-corona model where the source of $Λ$'s and $\overlineΛ$'s is taken as consisting of a high-density core and a less dense corona. We show that the overall properties of the polarization excitation functions can be linked to the relative abundance of $Λ$s coming from the core versus those coming from the corona. For low collision energies, the former are more abundant whereas for higher energies the latter become more abundant. The main consequence of this reversing of the relative abunda…
We report on measurements of directed flow as a function of pseudorapidity in Au+Au collisions at energies of $\sqrt{s_{_{NN}}} =$ 19.6, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density.
We report the measurement of the directed flow ($v_{1}$) for charged kaons in Au+Au collisions at $\sqrt{s_{NN}}$ =7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV as a function of rapidity and compare these results for pions, protons and antiprotons. These new kaon results may help to constrain the medium properties and collision dynamics including the in-medium kaon potential and baryon number transport in these collisions.
We report the measurements of spin alignment ($ρ_{00}$) for $K^{*0}$, $\overline{K^{*0}}$, $K^{*+}$, and $K^{*-}$ vector mesons in RHIC isobar collisions (Zr+Zr and Ru+Ru) at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. We observe the first non-zero spin alignment for $K^{*\pm}$ in heavy-ion collisions. The $K^{*\pm}$ $ρ_{00}$ is about 3.9$σ$ larger than that of $K^{*0}$. The observed difference and the ordering between $K^{*\pm}$ and $K^{*0}$ are surprising, and require further inputs from theory. When comparing between the isobar and Au+Au collisions, no significant system size dependence in $K^{*0}…
Anisotropic flow of K's, anti-K's, and lambdas is studied in heavy ion collisions at SPS and RHIC energies within the microscopic quark-gluon string model. At SPS energy the directed flow of kaons differs considerably at midrapidity from that of antikaons, while at RHIC energy kaon and antikaon flows coincide. The change is attributed to formation of dense meson-dominated matter at RHIC, where the differences in interaction cross-sections of hadrons become unimportant. The directed flows of strange particles, $v_1^{K,\bar{K}, Λ}(y)$, have universal negative slope at $|y| \leq 2$ at RHIC. The e…
PHOBOS measurements of elliptic flow are presented as a function of pseudorapidity, centrality, transverse momentum, energy and nuclear species. The elliptic flow in Cu-Cu is surprisingly large, particularly for the most central events. After scaling out the geometry through the use of an alternative form of eccentricity, called the participant eccentricity, which accounts for nucleon position fluctuations in the colliding nuclei, the relative magnitude of the elliptic flow in the Cu-Cu system is qualitatively similar to that measured in the Au-Au system.
We present the directed flow measurement ($v_1$) from Au+Au collisions at $\sqrtsNN = 62$ GeV. Over the pseudorapidity range we have studied, which covers $η$ from -1.2 to 1.2 and $2.4 < |η| < 4$, the magnitude of $v_1$ for charged particles is found to increase monotonously with pseudorapidity for all centralities. No ``$v_1$ wiggle'', as predicted by various theoretical models, is observed at midrapidity. Elliptic flow ($v_2$) from moderate high $p_t$ particles ($3-6 GeV/c$) at $\sqrtsNN = 200$ GeV is presented as a function of impact parameter. It is found that models that are based on {\it…
Rapidity-odd directed flow in heavy ion collisions can originate from two very distinct sources in the collision dynamics i. an initial tilt of the fireball in the reaction plane that generates directed flow of the constituents independent of their charges, and ii. the Lorentz force due to the strong primordial electromagnetic field that drives the flow in opposite directions for constituents carrying unlike sign charges. We study the directed flow of open charm mesons $D^0$ and $\overline{D^0}$ in the presence of both these sources of directed flow. The drag from the tilted matter dominates o…
In these proceedings, we present STAR measurements of directed flow, $v_{1}$, for pions, protons and antiprotons between $\sqrt{s_{NN}} = 7.7$ GeV and 200 GeV. A striking observation is that the $v_1$ slope for net protons as a function of rapidity, $F = dv_1/dy$, which is an estimate of the directed flow contribution from baryon number transported to the midrapidity region, changes sign twice within the lower part of this energy range. We also present the measured beam energy dependence of triangular flow $v_{3}$, and the $n=1$ to $n=5$ flow harmonics for charged particles at 200 GeV.
STAR's measurements of directed flow ($v_1$) around midrapidity for $π^{\pm}$, K$^{\pm}$, K$_S^0$, $p$ and $\bar{p}$ in Au + Au collisions at $\sqrtsNN = 200$ GeV are presented. A negative $v_1(y)$ slope is observed for most of produced particles ($π^{\pm}$, K$^{\pm}$, K$_{S}^{0}$ and $\bar{p}$). In 5-30% central collisions a sizable difference is present between the $v_1(y)$ slope of protons and antiprotons, with the former being consistent with zero within errors. The $v_1$ excitation function is presented. Comparisons to model calculations (RQMD, UrQMD, AMPT, QGSM with parton recombination,…
Directed flow ($v_1$) is a good probe of the early-stage dynamics of collision systems, and the $v_1$ slope at midrapidity ($dv_1/dy|_{y=0}$) is sensitive to the system's equation of state. STAR has published $v_1(y)$ measurements for ten particle species ($π^\pm$, $p$, $\bar{p}$, $Λ$, $\barΛ$, $ϕ$, $K^\pm$ and $K^0_{S}$) in Au+Au collisions at eight beam energies from $\sqrt{s_{NN}} = 7.7$ GeV to 200 GeV. In this study, we employ a simple coalescence idea to decompose $v_1$ of hadrons into $v_1$ of constituent quarks. The $dv_1/dy$ values of $\bar{p}$, $K^-$ and $\barΛ$ are used to test the c…
We present the first results using the STAR detector from the Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC). In this program, Au ion collisions at center of mass energies (\sqrt{s_{NN}}) of 7.7, 11.5 and 39 GeV allowed RHIC to extend the study of the QCD phase diagram from baryonic chemical potential values of 20 MeV to about 400 MeV. For the high net-baryon density matter at midrapidity, formed in these collisions, we report several interesting measurements. These include the observation of difference between anti-particle and particle elliptic flow, disappearan…
The results on directed and elliptic flow for Pb + Pb at the full energy of the SPS (158 GeV/A) and from the first year of Au + Au at RHIC (sqrt{s_{_{NN}}=130 GeV) are reviewed. The different experiments agree well and a consistent picture has emerged indicating early time thermalization at RHIC.
We report the elliptic flow ($v_{2}$) of $K_{s}^{0}$, $Λ$, $\barΛ$, $ϕ$, $Ξ^{-}$, and $\overlineΞ^{+}$ at mid-rapidity for Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The transverse momentum ($p_{T}$) and centrality dependence of $v_{2}$ have been studied. The number of constituent quark (NCQ) scaling for all the (multi-)strange hadrons has also been tested. The dependence in the ratio of average $v_{2}$ ($\langle$$v_{2}$$\rangle$) on centrality shows a deviation from unity indicating a difference in nuclear structure and deformation between the isobars. The results show…
Transverse momentum spectra of identified $π^{+}$, $π^{-}$, $K^{+}$, $K^{-}$, p and $\overline{p}$ were measured by the PHENIX experiment at mid-rapidity in Au-Au collisions at $\sqrt{s_{NN}}=130$ GeV over a broad momentum range. Inverse slope parameters and mean $p_{t}$ were measured in minimum bias events and as a function of the number of participating nucleons. The mass and centrality dependence of the inverse slope parameters and mean $p_{t}$ is presented and discussed.
Directed and elliptic event anisotropy parameters measured in the experiments at relativistic heavy-ion collider are presented. The possible origin of the measured elliptic anisotropy parameter $v_2$ and its sensitivity to the early phase of the high-energy heavy-ion collisions are discussed.
The study of flow can provide information on the initial state dynamics and the degree of equilibration attained in heavy ion collisions. This contribution presents results for both elliptic and directed flow as determined from data recorded by the PHOBOS experiment in Au+Au runs at RHIC at sqrt(sNN) = 19.6, 130 and 200 GeV. The PHOBOS detector provides a unique coverage in pseudorapidity for measuring flow at RHIC. The systematic dependence of flow on pseudorapidity, transverse momentum, centrality and energy is discussed.
We present results on pentaquark searches from nuclear collisions at RHIC with the STAR detector system. An intriguing peak has been observed in the invariant mass distribution of $pK^{+}+\overline{p}K^{-}$ from 18.6 Million d+Au collision events at $\sqrt{s_{_{NN}}} = 200$~GeV. The peak centers at a mass $1528 \pm 2 \pm 5$~MeV/c$^{2}$ and the FWHM $\sim15$ MeV/c$^{2}$ limited by detector responses. The statistical significance of the peak is $4.2σ$. Such a state if confirmed is manifestly exotic and implies a family of isospin one states. A weak signal of less statistical significance ($\sim3…
Anisotropic flow of kaons and antikaons is studied in heavy-ion collisions at CERN SPS and BNL RHIC energies within the microscopic quark-gluon string model. In the midrapidity range the directed flow of kaons v_1 differs considerably from that of antikaons at SPS energy (E_{lab} = 160 AGeV), while at RHIC energy (\sqrt{s} = 130 AGeV) the excitation functions of both, kaon and antikaon, flows coincide within the statistical error bars. The change is attributed to formation of dense meson-dominated matter at RHIC, where the differences in interaction cross-sections of kaons and antikaons become…
We extend our POWLANG transport setup for the modelling of heavy-flavour production in heavy-ion collisions to the case of full 3+1 simulations, dropping the approximation of longitudinal boost-invariance of the background medium. This enables us to provide predictions for observables for which the rapidity dependence is essential in order to obtain a non-vanishing signal, like the directed flow $v_1$, and to get reliable results also for kinematic distributions of heavy-flavour particles at forward rapidity. We compare our predictions with experimental data obtained in Au-Au and Pb-Pb collisi…
The property of the ``perfect liquid'' created at RHIC is probed with anisotropic flow measurements. Different initial conditions and their consequences on flow measurements are discussed. The collectivity is shown to be achieved fast and early. The thermalization is investigated with the ratio of $v_4/v_2^2$. Measurements from three sectors of soft physics (HBT, flow and strangeness) are shown to have a simple, linear, length scaling. Directed flow is found to be independent of system size.
The production of phi mesons in Au+Au collisions at RHIC and their propagation in a hot and dense nuclear medium is studied within the microscopic quark-gluon string model. The inverse slope parameter of the transverse mass distribution agrees well with that extracted from the STAR data, while the absolute yield of phi is underestimated by a factor 2. It appears that the fusion of strings alone cannot increase the phi yield either. Less than 30% of detectable phi's experience elastic scattering, this rate is insufficient for the full thermalization of phi. The directed flow of phi at |y|<2 dem…
The directed flow of particles produced in ultrarelativistic heavy ion collisions at SPS and RHIC is so small that currently available methods of analysis are at the border of applicability. Standard two-particle and flow-vector methods are biased by large nonflow correlations. On the other hand, cumulants of four-particle correlations, which are free from this bias, are plagued by large statistical errors. Here, we present a new method based on three-particle correlations, which uses the property that elliptic flow is large at these energies. This method may also be useful at intermediate ene…
We present the first measurement of directed flow ($v_1$) at the Relativistic Heavy Ion Collider (RHIC). $v_1$ is found to be consistent with zero at pseudorapidities $η$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |η| < 4$. The latter observation is similar to that from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. We studied the evolution of elliptic flow from p+p collisions through d+Au collision, and onto Au+Au collisions. Measurements of higher harmonics are presented and discussed.
Measurements of anisotropic flow in heavy-ion collisions provide insight into the early stage of the system's evolution. This proceedings presents directed and elliptic flow for Au+Au collisions at 39, 11.5 and 7.7 GeV, and for Cu+Cu at 22.4 GeV, measured in the STAR Experiment at RHIC. Differential measurements of directed and elliptic flow of charged particles as a function of centrality, transverse momentum and pseudorapidity are discussed.
Space-time picture of the anisotropic flow evolution in Au+Au collisions at BNL RHIC is studied for strange hadrons within the microscopic quark-gluon string model. The directed flow of both mesons and hyperons demonstrates wiggle structure with the universal antiflow slope at |y| < 2 for minimum bias events. This effect increases as the reaction becomes more peripheral. The development of both components of the anisotropic flow is closely related to particle freeze-out. Hadrons are emitted continuously, and different hadronic species are decoupled from the system at different times. These had…
We present a review of the measurements of elliptic flow ($v_{2}$) of light nuclei ($d$,$\bar{d}$, $t$, $^{3}\rm He$, and $^{3}\overline{\rm He}$) from the RHIC and LHC experiments. Light (anti)nuclei $v_{2}$ have been compared with that of (anti)proton. We observed a similar trend in light nuclei $v_{2}$ to that in identified hadron $v_{2}$ with respect to the general observations such as ($p_{\rm T}$) dependence, low $p_{\rm T}$ mass ordering, and centrality dependence. We also compared the difference of nuclei and antinuclei $v_{2}$ with the corresponding difference of $v_{2}$ of proton and…
Charged particle directed flow at midrapidity, |eta|<0.8, and forward rapidity, 1.7 < |eta|<5.1, is measured in Pb-Pb collisions at sqrt{s_NN} = 2.76 TeV with ALICE at the LHC. Directed flow is reported as a function of collision centrality, charged particle transverse momentum, and pseudo-rapidity. Results are compared to measurements at RHIC and recent model calculations for LHC energies.
We report the first observations of the first harmonic (directed flow, v_1), and the fourth harmonic (v_4), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v_2) generated at RHIC. From the correlation of v_2 with v_1 it is determined that v_2 is positive, or {\it in-plane}. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.
The global polarization of the $Λ$ and $\overlineΛ$ hyperons is measured for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum ($p_{\rm{T}}$) for the range of centrality 5-50%, $0.5 < p_{\rm{T}} <5$ GeV/$c$, and rapidity $|y|<0.5$. The hyperon global polarization averaged for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV is found to be consistent with zero, $\langle P_{\rm{H}}\rangle$ (%) $\approx$ - 0.01 $\pm$ 0.05 (stat.…
We construct a dynamical model for high-energy heavy-ion collision based on the relativistic resistive magneto-hydrodynamic framework. Using our newly developed (3+1)-dimensional relativistic resistive magneto-hydrodynamics code, we investigate magneto-hydrodynamic expansion in symmetric and asymmetric collision systems as a first application to high-energy heavy-ion collisions. As a realistic initial condition for electromagnetic fields, we consider the solutions of the Maxwell equations with the source term of point charged particles moving in the direction of the beam axis, including finite…
Following the Boz$\dot{\textrm{e}}$k-Wyskiel parametrization tilted initial condition, an alternative way to construct a longitudinal tilted fireball based on the Glauber collision geometry is presented. This longitudinal tilted initial condition combined with the Ideal-CLVisc (3 + 1)D hydrodynamic model, a nonvanishing directed flow coefficient $v_{1}$ in a wide rapidity range is observed. After comparing the model's results with experimentally observed data of directed flow coefficient $v_{1}(η)$ from $\sqrt{s_{NN}}$ = 200 GeV Cu + Cu, Au + Au collisions at RHIC energy to $\sqrt{s_{NN}}$ = 2…
The exploration of the QCD phase diagram has been one of the main drivers of contemporary nuclear physics. The Relativistic Heavy Ion Collider (RHIC) at BNL is uniquely suited for this task through its Beam Energy Scan (BES) program which allowed for a large range in baryon chemical potential $μ_B$ as was successfully demonstrated after the completion of Phase 1 in 2014. Phase 2 of the BES at RHIC is scheduled to start in 2019 and will explore with precision measurements the intermediate-to-high $μ_B$ region of the QCD phase diagram, five energies $\sqrt{s_{NN}}$ from 7.7 to 19.6 GeV in collid…
We report a new measurement of negatively charged pion directed flow $v_1$ relative to the spectator plane for Pb+Pb collisions at the beam energy 40A GeV recorded by the NA49 experiment at CERN. $v_1$ is reported as a function of rapidity and transverse momentum in different classes of collision centrality. The projectile spectator plane is estimated using transverse segmentation of the NA49 forward hadron calorimeter. The new results extend the NA49 data for $v_1$, which was previously measured only relative to the participant plane, and complement recent preliminary data by the NA61/SHINE c…
We analyze published data from the ALICE Collaboration in order to obtain the first extraction of the recently-proposed rapidity-even directed flow observable v1. An accounting of the correlation due to the conservation of transverse momentum restores the factorization seen by ALICE in all other Fourier harmonics and thus indicates that the remaining correlation gives a reliable measurement of directed flow. We then carry out the first viscous hydrodynamic calculation of directed flow, and show that it is less sensitive to viscosity than higher harmonics. This allows for a direct extraction of…
It has been proposed that strong electromagnetic fields produced in the early stages of heavy-ion collisions can lead to splitting of the rapidity-odd directed flow of positive and negative hadrons. For light hadrons, the interpretation of such measurements is complicated by the low magnitude of directed flow as well as by ambiguities arising from transported quarks. To overcome these complications, we propose measurements using only hadrons carrying produced quarks ($\bar{u},\bar{d},s,\bar{s}$). We discuss how to identify the kinematics where such hadrons are produced via the coalescence mech…
We present the directed flow ($v_1$) measured in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 62.4 GeV in the mid-pseudorapidity region $|η|<1.3$ and in the forward pseudorapidity region $2.5 < |η| < 4.0$. The results are obtained using the three-particle cumulant method, the event plane method with mixed harmonics, and for the first time at the Relativistic Heavy Ion Collider (RHIC), the standard method with the event plane reconstructed from spectator neutrons. Results from all three methods are in good agreement. Over the pseudorapidity range studied, charged particle directed flow is in the di…
We report the results of $v_1$ and $dv_1/dy$ near mid-rapidity for $Λ$, $\barΛ$, $K^{\pm}$, $K_s^0$ and $ϕ$ in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 11.5, 14.5, 19.6, 27 and 39~GeV using the STAR detector at RHIC. The $dv_1/dy$ of $Λ$ is found to be consistent with that of the proton and shows a change in sign near $\sqrt{s_{\rm NN}} = 11.5$~GeV. The $v_{1}$ slope for $\barΛ$, $\bar{p}$ and $ϕ$ shows a similar trend for $\sqrt{s_{\rm NN}}$ $>$ 14.5~GeV, while below 14.5~GeV, $ϕ$ $v_{1}$ is consistent with zero but with a large uncertainty. The $dv_{1}/dy$ for net protons and net kaons…
We study the origin of the directed flow of charged particles produced in relativistic heavy-ion collisions. Three different initial conditions, Boz$\dot{\textrm{e}}$k-Wyskiel, CCNU and Shen-Alzhrani, of energy density distributions are coupled to the (3+1)-dimensional viscous hydrodynamic model CLVisc, and their effects on the development of the anisotropic medium geometry, pressure gradient and radial flow are systematically compared. By comparing to experimental data at both RHIC and LHC, we find that the directed flow provides a unique constraint on the tilt of the initial medium profile i…
Two measurements related to the proton and anti-proton production near midrapidity in center of mass energies of 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV Au+Au collisions using the STAR detector at the Relativistic Heavy Ion Collider (RHIC) are discussed. At intermediate impact parameters the slope parameter of the directed flow versus rapidity (dv1/dy) for the net-protons shows a non-monotonic variation as a function of the beam energy. This non-monotonic variation is characterized by the presence of a minimum in dv1/dy between 11.5 and 19.6 GeV and a change in the sign of dv1/dy twice betwe…
We present the analyses of single electrons from semileptonic bottom and charm hadron decays at mid-rapidity in $\sqrt{s_{NN}}$ = 200 and 54.4 GeV Au+Au collisions (talk in Heavy-Flavor session III). The data at $\sqrt{s_{NN}}$ = 200 GeV incorporate information from the Heavy Flavor Tracker which enables the topological separation of electrons originating from bottom and charm hadron decays. We report the first STAR measurements at $\sqrt{s_{NN}}$ = 200 GeV of $v_{2}$ for bottom decay electrons as a function of $p_{T}$ and $v_{1}$ for charm decay electrons as a function of electron rapidity. A…
We present recent results from Al(beam)+Au(target) collisions at $\sqrt{s_{NN}}=4.9$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=4.5$\kern 0.16667em GeV from the STAR fixed-target (FXT) program. We report transverse mass spectra of protons, $K^0_S$ and $Λ$, rapidity density distributions of $π^\pm$, $K^0_S$ and $Λ$, directed flow of protons, $π^\pm$, $K^0_S$ and $Λ$, and elliptic flow of protons and $π^{\pm}$. These are the first measurements of pion directed and elliptic flow in this energy range at RHIC. Pion and proton elliptic flow show mass ordering. Measurements are compared with the publ…
Directed and elliptic flow are reported for charged pions and protons as a function of transverse momentum, rapidity, and centrality in 40 and 158 AGeV Pb + Pb collisions. The standard method of correlating particles with an event plane is used. The directed flow of protons is small and shows little variation near to midrapidity, but rises fast towards projectile rapidity in the 40 AGeV data. For most peripheral collisions the flat region becomes negative resulting in $v_1$ changing sign three times. Elliptic flow doesn't seem to change very much from 40 AGeV to 158 AGeV. The difference is sma…
