Details

Autor(en) / Beteiligte

• Abelev, B.I.
• Dunlop, J.
• et al. STAR Collaboration

Titel

Charged and strange hadron elliptic flow in Cu + Cu collisions at √sNN = 62.4 and 200 GeV

Ist Teil von

• Physical review. C, Nuclear physics, 2010-04, Vol.81 (4)

Ort / Verlag

United States

Erscheinungsjahr

2010

Quelle

American Physical Society [PROLA]

Beschreibungen/Notizen

• We present the results of an elliptic flow, v{sub 2}, analysis of Cu+Cu collisions recorded with the solenoidal tracker detector (STAR) at the BNL Relativistic Heavy Ion Collider at {radical}s{sub NN} = 62.4 and 200 GeV. Elliptic flow as a function of transverse momentum, v{sub 2}(p{sub T}), is reported for different collision centralities for charged hadrons h{sup {+-}} and strangeness-containing hadrons K{sub S}{sup 0}, {Lambda}, {Xi}, and {phi} in the midrapidity region |{eta}| < 1.0. Significant reduction in systematic uncertainty of the measurement due to nonflow effects has been achieved by correlating particles at midrapidity, |{eta}| < 1.0, with those at forward rapidity, 2.5 < |{eta}| < 4.0. We also present azimuthal correlations in p+p collisions at {radical}s = 200 GeV to help in estimating nonflow effects. To study the system-size dependence of elliptic flow, we present a detailed comparison with previously published results from Au+Au collisions at {radical}s{sub NN} = 200 GeV. We observe that v{sub 2}(p{sub T}) of strange hadrons has similar scaling properties as were first observed in Au+Au collisions, that is, (i) at low transverse momenta, p{sub T} < 2 GeV/c, v{sub 2} scales with transverse kinetic energy, m{sub T}-m, and (ii) at intermediate p{sub T}, 2 < p{sub T} < 4 GeV/c, it scales with the number of constituent quarks, n{sub q}. We have found that ideal hydrodynamic calculations fail to reproduce the centrality dependence of v{sub 2}(p{sub T}) for K{sub s}{sup 0} and {Lambda}. Eccentricity scaled v{sub 2} values, v{sub 2}/{var_epsilon}, 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{sub 2}/{var_epsilon} depends on the system size, that is, the number of participants N{sub part}. This indicates that the ideal hydrodynamic limit is not reached in Cu+Cu collisions, presumably because the assumption of thermalization is not attained.