System size dependence of elliptic flows in relativistic heavy-ion collisions

We study the elliptic flow systematically from SIS to RHIC energies in a realistic dynamical cascade model. We compile our results with the recent data from STAR and PHOBOS experiments on elliptic flow of charged particles in Au + Au collisions at RHIC energy. From the analysis of elliptic flow as a function of different dynamical variables such as transverse momenta, pseudorapidity and centrality at RHIC energy, we found a good fitting with data at 1.5 times a scaling factor...

Please note that after these results were reported at Quark Matter 2006 and posted on the preprint server it was found that what is reported here as \textit{elliptic flow fluctuations}, should rather be taken as an upper limit on the fluctuations. Further analysis has shown that fitting the multiplicity dependence of the q-distribution does not enable one to disentangle non-flow and fluctuations. The data from the q-vector distrubution does not, therefore, exclude the case of...

We have measured the proton elliptic flow excitation function for the Au + Au system spanning the beam energy range 2 -- 8 AGeV. The excitation function shows a transition from negative to positive elliptic flow at a beam energy, $E_{tr} \sim$ 4 AGeV. Detailed comparisons with calculations from a relativistic Boltzmann-equation are presented. The comparisons suggest a softening of the nuclear equation of state (EOS) from a stiff form (K \sim 380 MeV) at low beam energies (E_{...

Recent PHENIX elliptic flow ($v_2$) measurements for identified particles produced in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV are presented and compared to other RHIC measurements. They indicate universal scaling of $v_2$ compatible with partonic collectivity leading to the flow of light, strange and heavy quarks with a common expansion velocity field.

Using the perturbative method for the simulation of charmed particles, the dynamical origin of charm quark elliptic flow is studied in the framework of a multi-phase transport (AMPT) model. Besides the expected ordering relative to that of light quarks according to quark masses, charm quark elliptic flow is seen to be sensitive to the parton scattering cross section. To describe the observed large elliptic flow of electrons from the decay of charmed mesons, a charm quark elas...

We interpret the scaling of the corrected elliptic flow parameter w.r.t. the corrected multiplicity, observed to hold in heavy ion collisions for a wide variety of energies and system sizes. We use dimensional analysis and power-counting arguments to place constraints on the changes of initial conditions in systems with different center of mass energy $\sqrt{s}$. Specifically, we show that a large class of changes in the (initial) equation of state, mean free path, and longit...

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, transve...

We present first results on event-by-event elliptic flow fluctuations in Au+Au collisions at 200 GeV obtained with the PHOBOS detector. Over the measured range in centrality, large relative fluctuations of 40--50% are found. The elliptic flow fluctuations are well described as being proportional to fluctuations in the shape of the initial collision region, as estimated event-by-event with the participant eccentricity using Glauber Monte Carlo.

The common interpretation of elliptic flow $v_2$ in heavy ion collisions is that it is produced by hydrodynamic flow at low transverse momentum and by parton energy loss at high transverse momentum. Here, we discuss this interpretation in view of the dependence of $v_2$ with energy, rapidity and system size, and show that it is far from clear how the relevant properties necessary for this interpretation, low viscosity and high opacity, turn on. A low energy collider such as N...

Within the framework of a multiphase transport (AMPT) model that includes both initial partonic and final hadronic interactions, we show that including mean-field potentials in the hadronic phase leads to a splitting of the elliptic flows of particles and their antiparticles, providing thus a plausible explanation of the different elliptic flows between $p$ and ${\bar p}$, $K^+$ and $K^-$, and $\pi^+$ and $\pi^-$ observed in recent Beam Energy Scan (BES) program at the Relati...