Partonic Flow and $\varphi$-Meson Production in $\mathrm{Au}+\mathrm{Au}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$

We present first measurements of the $\varphi$-meson elliptic flow ($v_2(p_T)$) and high-statistics $p_T$ distributions for different centralities from $\sqrt{s_{NN}}=200\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC. In minimum bias collisions the $v_2$ of the $\varphi$ meson is consistent with the trend observed for mesons. The ratio of the yields of the $\Omega$ to those of the $\varphi$ as a function of transverse momentum is consistent with a model based on the recombination of thermal $s$ quarks up to $p_T\sim 4\mathrm{GeV}/c$, but disagrees at higher momenta. The nuclear modification factor ($R_{\mathrm{CP}}$) of $\varphi$ follows the trend observed in the $K_S^0$ mesons rather than in $\Lambda$ baryons, supporting baryon-meson scaling. These data are consistent with $\varphi$ mesons in central $\mathrm{Au}+\mathrm{Au}$ collisions being created via coalescence of thermalized $s$ quarks and the formation of a hot and dense matter with partonic collectivity at RHIC.

Figure 1

Top panel: The elliptic flow, $v_2(p_T)$, for the $\varphi$-meson as a function of centrality. The vertical error bars represent the statistical errors while the shaded bands represent the systematic uncertainties. For clarity, data points are shifted slightly in $p_T$. Bottom panel: Minimum bias $v_2(p_T)$ for the $\varphi$-meson compared to results for $\Lambda$ and $K_S^0$ [12]. The dashed and dotted lines represent parameterizations inspired by number-of-quark scaling ideas from Ref. [29] for $\mathrm{NQ}=2$ and $\mathrm{NQ}=3$, respectively.

Figure 2

Transverse momentum distributions of $\varphi$-mesons from $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. For clarity, distributions for different centralities are scaled by factors of ten. Dashed lines represent the exponential fits to the distributions and the dotted lines are Levy function fits. Error bars represent statistical errors only.

Figure 3

The $N(\Omega )/N(\varphi )$ ratio vs $p_T$ for three centrality bins in $\sqrt{s_{NN}}=200\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions. The solid and dashed lines represent recombination model predictions for central collisions [22] for total and thermal contributions, respectively. Note for the most central collision, the data of $\varphi$ are $\Omega$ are from top 12% and 10%, respectively.

Figure 4

The $R_{\mathrm{CP}}$ of midrapidity $\varphi$-mesons produced in $\sqrt{s_{NN}}=200\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ collisions: (top) 0%–5% vs 40%–60% and (bottom) 0%–5% vs 60%–80% The shaded bands represent the uncertainties in the Glauber model calculations for $⟨N_{\mathrm{bin}}⟩$ and $⟨N_{\mathrm{part}}⟩$ [36]. Also shown are results for $\Lambda$ and $K_S^0$ [12] and protons and ${\pi }^{+}$ [37].