Centrality and Transverse Momentum Dependence of Elliptic Flow of Multistrange Hadrons and $\varphi$ Meson in $\mathrm{Au}+\mathrm{Au}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$

We present high precision measurements of elliptic flow near midrapidity ($|y|<1.0$) for multistrange hadrons and $\varphi$ meson as a function of centrality and transverse momentum in $\mathrm{Au}+\mathrm{Au}$ collisions at center of mass energy $\sqrt{s_{NN}}=200\mathrm{GeV}$. We observe that the transverse momentum dependence of $\varphi$ and $\mathrm{\Omega }$ $v_2$ is similar to that of $\pi$ and $p$, respectively, which may indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. Number of constituent quark scaling is found to hold within statistical uncertainty for both 0%–30% and 30%–80% collision centrality. There is an indication of the breakdown of previously observed mass ordering between $\varphi$ and proton $v_2$ at low transverse momentum in the 0%–30% centrality range, possibly indicating late hadronic interactions affecting the proton $v_2$.

Figure 1

The $v_2$ as a function of $p_T$ near midrapidity ($|y|<1.0$) for (a) ${\mathrm{\Xi }}^{-}+{\overline{\mathrm{\Xi }}}^{+}$, (b) ${\mathrm{\Omega }}^{-}+{\overline{\mathrm{\Omega }}}^{+}$, and (c) $\varphi$ from $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ for 0%–30% and 30%–80% centrality. The systematic uncertainties are shown with shaded boxes and the statistical uncertainties by vertical lines.

Figure 2

The $v_2$ as a function of $p_T$ for (a) $\pi$, $p$ and (b) $\varphi$, $\mathrm{\Omega }$ from minimum-bias $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ for 0%–80% centrality. The systematic uncertainties are shown with the shaded boxes, while vertical lines represent the statistical uncertainties.

Figure 3

Panel (a) and (b) show $v_2$ scaled by number of constituent quarks ($n_q$) as a function of $p_T/n_q$ for 0–30% and 30–80% collision centrality, respectively. Panel (c) and (d) show $v_2$ scaled by number of constituent quarks ($n_q$) as a function of ($(m_T-m_0)/n_q$ for 0–30% and 30–80% collision centrality, respectively. Ratios with respect to a polynomial fit to the $K_S^0$ $v_2$ are shown in the corresponding lower panels. Vertical lines are statistical uncertainties and shaded boxes are systematic uncertainties.

Figure 4

$v_2(\varphi )/v_2(p)$ ratio as a function of $p_T$ for 0%–30%, 30%–80%, and 0%–80% centrality in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. Shaded boxes are the systematic uncertainties and vertical lines are the statistical uncertainties. The first data point of 0%–80% centrality is shifted to the right by $400\mathrm{MeV}/c$. The bands in (a) and (b) represent the hydro model [8] and transport model calculations, respectively, for $v_2(\varphi )/v_2(p)$.