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Energy and system size dependence of phi meson production in Cu+Cu and Au+Au collisions

The collaboration
Phys.Lett.B 673 (2009) 183-191, 2009.

Abstract (data abstract)
We study the beam-energy and system-size dependence of $\phi$ meson production (using the hadronic decay mode $\phi \to K^{+}K^{-}$) by comparing the new results from $Cu+Cu$ collisions and previously reported $Au+Au$ collisions at $\sqrt{s_{NN}}=62.4$ and 200 GeV measured in the STAR experiment at RHIC. Data presented in this Letter are from mid-rapidity $(|y| < 0.5)$ for $0.4 < p_{T} < 5$ GeV/$c$. At a given beam energy, the transverse momentum distributions for $\phi$ mesons are observed to be similar in yield and shape for $Cu+Cu$ and $Au+Au$ colliding systems with similar average numbers of participating nucleons. The $\phi$ meson yields in nucleus-nucleus collisions, normalized by the average number of participating nucleons, are found to be enhanced relative to those from $p+p$ collisions. The enhancement for $\phi$ mesons lies between strange hadrons having net strangeness = 1 ($K^{−}$ and $\bar{\Lambda}$) and net strangeness = 2 ($\Xi$). The enhancement for $\phi$ mesons is observed to be higher at $\sqrt{s_{NN}}=200$ GeV compared to 62.4 GeV. These observations for the produced $\phi (s\bar{s})$ mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.

• #### Table 1a

Data from Fig. 2, left panel

10.17182/hepdata.101351.v1/t1

Midrapidity $(|y| < 0.5)$ transverse momentum spectra of $\phi$ mesons for various collision centrality classes for $Cu+Cu$ collisions at $\sqrt{s_{NN}}=62.4$...

• #### Table 1b

Data from Fig. 2, right panel

10.17182/hepdata.101351.v1/t2

Midrapidity $(|y| < 0.5)$ transverse momentum spectra of $\phi$ mesons for various collision centrality classes for $Cu+Cu$ collisions at $\sqrt{s_{NN}}=62.4$...

• #### Table 2a

Data from Fig. 4, upper panels, 0-10%

10.17182/hepdata.101351.v1/t3

Upper panels. $N_{\scriptsize{\mbox{part}}}$ scaled ($R^{N_{\scriptsize{\mbox{part}}}}_{AA}$) nuclear modification factors as a function of $p_{T}$ of $\phi$ mesons for $0-10\%$ and $20-30\%$...

• #### Table 2b

Data from Fig. 4, upper panels, 20-30%

10.17182/hepdata.101351.v1/t4

Upper panels. $N_{\scriptsize{\mbox{part}}}$ scaled ($R^{N_{\scriptsize{\mbox{part}}}}_{AA}$) nuclear modification factors as a function of $p_{T}$ of $\phi$ mesons for $0-10\%$ and $20-30\%$...

• #### Table 2c

Data from Fig. 4, lower panels, 0-10%

10.17182/hepdata.101351.v1/t5

Upper panels. $N_{\scriptsize{\mbox{part}}}$ scaled ($R^{N_{\scriptsize{\mbox{part}}}}_{AA}$) nuclear modification factors as a function of $p_{T}$ of $\phi$ mesons for $0-10\%$ and $20-30\%$...

• #### Table 2d

Data from Fig. 4, lower panels, 20-30%

10.17182/hepdata.101351.v1/t6

Upper panels. $N_{\scriptsize{\mbox{part}}}$ scaled ($R^{N_{\scriptsize{\mbox{part}}}}_{AA}$) nuclear modification factors as a function of $p_{T}$ of $\phi$ mesons for $0-10\%$ and $20-30\%$...

• #### Table 3a

Data from Fig. 5, upper panel

10.17182/hepdata.101351.v1/t7

Upper panel. The ratio of the yields of $K^{−}$, $\phi$, $\bar{\Lambda}$ and $\Xi+\bar{\Xi}$ normalized to $N_{\scriptsize{\mbox{part}}}$ in nucleus-nucleus collisions to...

• #### Table 3b

Data from Fig. 5, lower panel

10.17182/hepdata.101351.v1/t8

Upper panel. The ratio of the yields of $K^{−}$, $\phi$, $\bar{\Lambda}$ and $\Xi+\bar{\Xi}$ normalized to $N_{\scriptsize{\mbox{part}}}$ in nucleus-nucleus collisions to...