Scaling Properties of Hyperon Production in $\mathrm{Au}+\mathrm{Au}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$

We present the scaling properties of $\Lambda$, $\Xi$, and $\Omega$ in midrapidity $\mathrm{Au}+\mathrm{Au}$ collisions at the Brookhaven National Laboratory Relativistic Heavy Ion Collider at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The yield of multistrange baryons per participant nucleon increases from peripheral to central collisions more rapidly than that of $\Lambda$, indicating an increase of the strange-quark density of the matter produced. The strange phase-space occupancy factor ${\gamma }_s$ approaches unity for the most central collisions. Moreover, the nuclear modification factors of $p$, $\Lambda$, and $\Xi$ are consistent with each other for $2<p_T<5\mathrm{GeV}/c$ in agreement with a scenario of hadron formation from constituent quark degrees of freedom.

Figure 1

Transverse momentum distributions of (a) $\Lambda (\overline{\Lambda })$ for $|y|<1.0$, (b) ${\Xi }^{-}({\overline{\Xi }}^{+})$ for $|y|<0.75$, and (c) ${\Omega }^{-}+{\overline{\Omega }}^{+}$ for $|y|<0.75$ in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ as a function of centrality. Scale factors were applied to the spectra for clarity. Only statistical errors are shown. The dashed curves show a Boltzmann fit to the $\Lambda$, ${\Xi }^{-}$, and ${\Omega }^{-}+{\overline{\Omega }}^{+}$ data; the fits to the $\overline{\Lambda }$ and ${\overline{\Xi }}^{+}$ are omitted for clarity.

Figure 2

(a) The integrated yield $dN/dy$ at midrapidity for ${\overline{\Xi }}^{+}$, $\overline{\Lambda }$, and $\overline{p}$ divided by $N_{\mathrm{part}}$, normalized to the most peripheral collisions (60%–80%), plotted as a function of $N_{\mathrm{part}}$. The gray, black, and dashed bands represent the errors on the normalization to the bin 60%–80% for ${\overline{\Xi }}^{+}$, $\overline{\Lambda }$, and $\overline{p}$, respectively. Other errors shown are statistical only. (b) ${\gamma }_s$ as a function of $N_{\mathrm{part}}$ for $\mathrm{Au}+\mathrm{Au}$ collisions at 200 GeV (cf. text for details). Values for $e^{+}+e^{-}$, $p+\overline{p}$, and $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=91$, 200, and 17.2 GeV, respectively, are shown for comparison [26, 27, 28].

Figure 3

$R_{CP}$ for ${\Xi }^{-}+{\overline{\Xi }}^{+}$ and ${\Omega }^{-}+{\overline{\Omega }}^{+}$ at midrapidity (0%–5% vs 40%–60%). A dashed line for charged hadrons and a gray band for $\Lambda +\overline{\Lambda }$ are shown for comparison. The gray rectangles represent participant and binary scalings.