Charged and strange hadron elliptic flow inCu+Cucollisions atsNN=

Abstract

We present the results of an elliptic flow, v 2 , analysis of Cu + Cu collisions recorded with the solenoidal tracker detector (STAR) at the BNL Relativistic Heavy Ion Collider at √ s NN = 62.4 and 200 GeV. Elliptic flow as a function of transverse momentum, v 2 (p T ), is reported for different collision centralities for charged hadrons h ± and strangeness-ontaining hadrons K 0 S , , , and φ in the midrapidity region |η| < 1.0. Significant reduction in systematic uncertainty of the measurement due to nonflow effects has been achieved by correlating particles at midrapidity, |η| < 1.0, with those at forward rapidity, 2.5 < |η| < 4.0. We also present azimuthal correlations in p + p collisions at (2010) energy, m T − m, and (ii) at intermediate p T , 2 < p T < 4 GeV/c, it scales with the number of constituent quarks, n q . We have found that ideal hydrodynamic calculations fail to reproduce the centrality dependence of v 2 (p T ) for K 0 S and . Eccentricity scaled v 2 values, v 2 /ε, are larger in more central collisions, suggesting stronger collective flow develops in more central collisions. The comparison with Au + Au collisions, which go further in density, shows that v 2 /ε depends on the system size, that is, the number of participants N part . This indicates that the ideal hydrodynamic limit is not reached in Cu + Cu collisions, presumably because the assumption of thermalization is not attained.

Elliptic and triangular flow of identified particles from the AMPT model at RHIC energies

“…At low transverse momenta (p T < 2.0 GeV/c), a mass ordering of v 2 (p T ) was observed [5,6], which can be understood within a hydrodynamic framework [7]. At intermediate transverse momenta (2.0 < p T < 6.0 GeV/c), a Number-of-Constituent Quark (NCQ) scaling [8] was observed [9][10][11][12]. The NCQ scaling was used to conclude that the relevant degrees of freedom in the created matter are quarks and gluons.…”

Inclusive charged hadron elliptic flow in Au+Au collisions atsNN=7.7–39 GeV

“…The event planes are determined from the TPC in the midrapidity region, and the FTPC/BBC at forward rapidity. The η gap between FTPC/BBC to TPC could reduce the nonflow contribution in the v 2 measurement [13]. Figure 2 Owing to limited statistics, the FTPC event plane is used only for the 39-GeV data set where the BBC event plane cannot be used because of the poor resolution.…”

“…The centrality dependence of p T differential v 2 with respect to the initial eccentricity has been studied in detail for Au + Au and Cu + Cu collisions in √ s NN = 200 and 62.4 GeV [12,13]. The larger magnitude of v 2 in the more peripheral collisions could be attributable to the larger initial eccentricity in coordinate space for the more peripheral collisions.…”

“…In a picture of hydrodynamic expansion of the system formed in the collisions, these anisotropies are expected to arise owing to initial pressure gradients and subsequent interactions of the constituents [4,5]. Specifically, differential measurements [6][7][8][9][10][11][12][13][14][15][16][17][18][19] of azimuthal anisotropy have been found to be sensitive to (a) the equation of state (EOS), (b) thermalization, (c) transport coefficients of the medium, and (d) initial conditions in the heavy-ion collisions. Hence, it is important to study the dependence of azimuthal anisotropy as a function of several variables, for example center-of-mass energy ( √ s NN ), collision centrality, transverse momentum (p T ), and pseudorapidity (η).…”

System size and energy dependence of near-side dihadron correlations

“…[49]. The nominal value is given by v 2 from the event-plane method using the forward TPCs for the determination of the event plane and the upper bound is from the statistical error for both √ s NN = 62.4 GeV and 200 GeV.…”