Evolution of the nuclear modification factors with rapidity and centrality in d+Au collisions at $\sqrt{s_{NN}} = 200 GeV

TL;DR

A significant and systematic decrease of R(dAu) is found with increasing rapidity for charged hadrons produced in deuteron + gold collisions at sqrt[s(NN)]=200 GeV, as a function of collision centrality and of the pseudorapidity.

Abstract

We report on a study of the transverse momentum dependence of nuclear modification factors $R_{dAu}$ for charged hadrons produced in deuteron + gold collisions at $\sqrt{s_{NN}}= 200$GeV, as a function of collision centrality and of the pseudorapidity ($η= 0,1,2.2,3.2$) of the produced hadrons. We find significant and systematic decrease of $R_{dAu}$ with increasing rapidity. The midrapidity enhancement and the forward rapidity suppression are more pronounced in central collisions relative to peripheral collisions. These results are relevant to the study of the possible onset of gluon saturation at RHIC energies.

Figures (4)

• Figure 1: Bottom row: Invariant yield distributions for charged hadrons produced in d+Au and p+p collisions at $\sqrt{s} = \unit[200]{GeV}$ at pseudorapidities $\eta=0,1.0,2.2,3.2$. Horizontal lines indicate bin width. Top row: Outline of the data samples in $\eta$ vs $p_T$ collected with the BRAHMS spectrometers at the various angle and magnetic field settings (shifted in $\eta$), gray lines are used to indicate the overlap of the settings. The dotted lines indicate the cuts applied in $\eta$.
• Figure 2: Nuclear modification factor for charged hadrons at pseudorapidities $\eta=0,1.0,2.2,3.2$. One standard deviation statistical errors are shown with error bars. Systematic errors are shown with shaded boxes with widths set by the bin sizes. The shaded band around unity indicates the estimated error on the normalization to $\langle N_{coll} \rangle$. Dashed lines at $p_T<1.5$ GeV/ c show the normalized charged particle density ratio $\frac{1}{\langle N_{coll}\rangle}\frac{dN/d\eta(Au)}{dN/d\eta(pp)}$.
• Figure 3: Central (full points) and semi-central (open points) $R_{cp}$ ratios (see text for details) at pseudorapidities $\eta=0,1.0,2.2,3.2$. Systematic errors ($\sim5\%$) are smaller than the symbols.
• Figure 4: Evolution of the central/peripheral (full points) and semicentral/peripheral (open points) $R_{cp}$ ratios on pseudorapidity.