Identified Baryon and Meson Distributions at Large Transverse Momenta from $\mathrm{Au}+\mathrm{Au}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$

Transverse momentum spectra of ${\pi }^{\pm }$, $p$, and $\overline{p}$ up to $12\mathrm{GeV}/c$ at midrapidity in centrality selected $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ are presented. In central $\mathrm{Au}+\mathrm{Au}$ collisions, both ${\pi }^{\pm }$ and $p(\overline{p})$ show significant suppression with respect to binary scaling at $p_T\gtrsim 4\mathrm{GeV}/c$. Protons and antiprotons are less suppressed than ${\pi }^{\pm }$, in the range $1.5\lesssim p_T\lesssim 6\mathrm{GeV}/c$. The ${\pi }^{-}/{\pi }^{+}$ and $\overline{p}/p$ ratios show at most a weak $p_T$ dependence and no significant centrality dependence. The $p/\pi$ ratios in central $\mathrm{Au}+\mathrm{Au}$ collisions approach the values in $p+p$ and $d+\mathrm{Au}$ collisions at $p_T\gtrsim 5\mathrm{GeV}/c$. The results at high $p_T$ indicate that the partonic sources of ${\pi }^{\pm }$, $p$, and $\overline{p}$ have similar energy loss when traversing the nuclear medium.

Figure 1

Centrality dependence of midrapidity ($|y|<0.5$) ${\pi }^{\pm }$, $p$, and $\overline{p}$ invariant yields versus $p_T$ from 200 GeV $\mathrm{Au}+\mathrm{Au}$ collisions. The error bars are the quadrature sum of statistical and systematic errors. The solid lines depict our best estimates of the proton yields corrected for the hyperon ($\Lambda$ and ${\Sigma }^{+}$) feed-down [25]. The shaded bands on the lines represent the uncertainties. The order of the spectra in different centralities is the same for both panels.

Figure 2

Nuclear modification factors $R_{CP}$ for ${\pi }^{+}+{\pi }^{-}$ and $p+\overline{p}$ in 200 GeV $\mathrm{Au}+\mathrm{Au}$ collisions. The point-to-point systematic uncertainties are shown as the shaded boxes around the data points. The dark shaded bands show the normalization systematic uncertainty in the number of binary collisions. The solid lines show jet quenching predictions for pions [27].

Figure 3

The ${\pi }^{-}/{\pi }^{+}$ and $\overline{p}/p$ ratios in 12% central, MB $\mathrm{Au}+\mathrm{Au}$ and $d+\mathrm{Au}$ [21, 22] collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The shaded boxes represent the systematic uncertainties in the top 12% central $\mathrm{Au}+\mathrm{Au}$ collisions. The systematic uncertainties for MB $\mathrm{Au}+\mathrm{Au}$ collisions are similar. Curves are the corresponding predictions from a jet quenching model [4].

Figure 4

The $p/{\pi }^{+}$ and $\overline{p}/{\pi }^{-}$ ratios from $d+\mathrm{Au}$ [21, 22] and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The $(p+\overline{p})/({\pi }^{+}+{\pi }^{-})$ ratio from light quark jets in $e^{+}+e^{-}$ collisions at $\sqrt{s}=91.2\mathrm{GeV}$ is shown as a dotted-dashed line [29]. The shaded boxes represent the systematic uncertainties in the top 12% central $\mathrm{Au}+\mathrm{Au}$ collisions. The systematic uncertainties for 60%–80% $\mathrm{Au}+\mathrm{Au}$ collisions are similar. The dotted and dashed lines are model calculations in central $\mathrm{Au}+\mathrm{Au}$ collisions [12, 13].