/ nucl-ex arXiv:1412.1043

Systematic Study of Azimuthal Anisotropy in Cu$+$Cu and Au$+$Au Collisions at $\\sqrt{s_{_{NN}}} = 62.4$ and 200~GeV

Pages: 22

Abstract: We have studied the dependence of azimuthal anisotropy $v_2$ for inclusive and identified charged hadrons in Au$+$Au and Cu$+$Cu collisions on collision energy, species, and centrality. The values of $v_2$ as a function of transverse momentum $p_T$ and centrality in Au$+$Au collisions at $\\sqrt{s_{_{NN}}}$=200~GeV and 62.4~GeV are the same within uncertainties. However, in Cu$+$Cu collisions we observe a decrease in $v_2$ 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 $v_2$ depends both on eccentricity and the number of participants, $N_{\\rm part}$. We observe that $v_2$ divided by eccentricity ($\\varepsilon$) monotonically increases with $N_{\\rm part}$ and scales as ${N_{\\rm part}^{1/3}}$. The Cu$+$Cu data at 62.4 GeV falls below the other scaled $v_{2}$ data. For identified hadrons, $v_2$ divided by the number of constituent quarks $n_q$ is independent of hadron species as a function of transverse kinetic energy $KE_T=m_T-m$ between $0.1<KE_T/n_q<1$~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 $v_2/(n_q\\cdot\\varepsilon\\cdot N^{1/3}_{\\rm part})$ vs $KE_T/n_q$ for all measured particles.

Note: *Brief entry*; *Temporary entry*; 424 authors, 22 pages, 22 figures, 6 tables. Submitted to Phys. Rev. C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html

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Запись создана 2015-01-12, последняя модификация 2015-01-12

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