Systematic Study of Azimuthal Anisotropy in Cu+Cu and Au+Au Collisions at √sNN=62.4 and 200 GeV

Adare, A. and Afanasiev, S. and Aidala, C. and Ajitanand, N. N. and Akiba, Y. and Csanád, Máté and Csörgő, Tamás and Dávid, Gábor and Kiss, Ádám and Ster, András and Sziklai, János István and Tarján, Péter and Vértesi, Róbert and Zimányi, József (2015) Systematic Study of Azimuthal Anisotropy in Cu+Cu and Au+Au Collisions at √sNN=62.4 and 200 GeV. PHYSICAL REVIEW C, 92 (3). ISSN 2469-9985

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Abstract

We have studied the dependence of azimuthal anisotropy v2 for inclusive and identified charged hadrons in Au+Au and Cu+Cu collisions on collision energy, species, and centrality. The values of v2 as a function of transverse momentum pT and centrality in Au+Au collisions at √sN N =200 GeV and 62.4 GeV are the same within uncertainties. However, in Cu+Cu collisions we observe a decrease in v2 values as the collision energy is reduced from 200 to 62.4 GeV. The decrease is larger in the more peripheral collisions. By examining both Au+Au and Cu+Cu collisions we find that v2 depends both on eccentricity and the number of participants, Npart. We observe that v2 divided by eccentricity (ε) monotonically increases with Npart and scales as N 1/3 part. The Cu+Cu data at 62.4 GeV falls below the other scaled v2 data. For identified hadrons, v2 divided by the number of constituent quarks nq is independent of hadron species as a function of transverse kinetic energy KET = mT − m between 0.1 < KET /nq < 1 GeV. Combining all of the above scaling and normalizations, we observe a near-universal scaling, with the exception of the Cu+Cu data at 62.4 GeV, of v2/(nq · ε · N 1/3 part) vs KET /nq for all measured particles.

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