Centrality Dependence of Charged-Hadron Transverse-Momentum Spectra in $d+\mathrm{A}\mathrm{u}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$

We have measured transverse momentum distributions of charged hadrons produced in $d+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$. The spectra were obtained for transverse momenta $0.25<p_T<6.0\mathrm{G}\mathrm{e}\mathrm{V}/c$, in a pseudorapidity range of $0.2<\eta <1.4$ in the deuteron direction. The evolution of the spectra with collision centrality is presented in comparison to $p+\overline{p}$ collisions at the same collision energy. With increasing centrality, the yield at high transverse momenta increases more rapidly than the overall particle density, leading to a strong modification of the spectral shape. This change in spectral shape is qualitatively different from observations in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at the same energy. The results provide important information for discriminating between different models for the suppression of high-$p_T$ hadrons observed in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions.

Figure 1

Invariant yield of charged hadrons, $\frac{h^{+}+h^{-}}{2}$, as a function of $p_T$ for four centrality bins. Only statistical errors are shown.

Figure 2

The relative yield of $d+\mathrm{A}\mathrm{u}$ to UA1 $p+\overline{p}$ data at $p_T=1$, 2, 3, and $4\mathrm{G}\mathrm{e}\mathrm{V}/c$ is shown as a function of the integrated yield $dN/d\eta$ for the four $E_{\mathrm{r}\mathrm{i}\mathrm{n}\mathrm{g}}$ centrality bins. The ratio $d+\mathrm{A}\mathrm{u}/p+\overline{p}$ has been normalized to unity at $p_T=0.5\mathrm{G}\mathrm{e}\mathrm{V}/c$. The triangles indicate the values for $p+\overline{p}$. The brackets indicate the systematic errors on the relative yield (90% C.L.). The systematic error on $dN/d\eta$ is 12%.

Figure 3

Nuclear modification factor $R_{d\mathrm{A}\mathrm{u}}$ as a function of $p_T$ for four bins of centrality. For the most central bin, the spectral shape for central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ data relative to $p+\overline{p}$ is shown for comparison. The shaded area shows the uncertainty in $R_{d\mathrm{A}\mathrm{u}}$ due to the systematic uncertainty in $⟨N_{\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{l}}⟩$ and the UA1 scale error (90% C.L.). The brackets show the systematic uncertainty of the $d+\mathrm{A}\mathrm{u}$ spectra measurement (90% C.L.).

Figure 4

Nuclear modification factor $R_{d\mathrm{A}\mathrm{u}}$ as a function of centrality in four bins of transverse momentum. The brackets indicate the point-to-point systematic error, dominated by the uncertainty in the number of collisions for each centrality bin. The grey band shows the overall scale uncertainty at each $p_T$. Systematic errors are at 90% C.L.