Cold Nuclear Matter Effects on J/psi Yields as a Function of Rapidity and Nuclear Geometry in Deuteron-Gold Collisions at sqrt(s_NN) = 200 GeV

TL;DR

Measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200  GeV recorded by the PHENIX experiment are presented and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects.

Abstract

We present measurements of J/psi yields in d+Au collisions at sqrt(s_NN) = 200 GeV recorded by the PHENIX experiment and compare with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/psi rapidity (-2.2 < y < 2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. To remove model dependent systematic uncertainties we also compare the data to a simple geometric model. We find that calculations where the nuclear modification is linear or exponential in the density weighted longitudinal thickness are difficult to reconcile with the forward rapidity data.

Figures (3)

• Figure 1: (color online) (a) $\hbox{$J/\psi$}\xspace$$B_{ll}$$dN/dy$ in $p$+$p$ and d+ Au collisions as a function of rapidity. The d+ Au yields are divided by the average number of nucleon-nucleon collisions $\left< N_{\rm coll}(0\hbox{-}100\%)\right>$ = 7.6. (error lines) point-to-point uncorrelated uncertainties; (boxes) point-to-point correlated uncertainties; (text) global normalization scale uncertainties. (b) $R_{d\rm{Au}}$ nuclear modification factors for unbiased collisions.
• Figure 2: (color online) Nuclear suppression factors ($R_{d\rm{Au}}$) for (a) peripheral, (b) central, and (c) $R_{\rm CP}$ as a function of rapidity.
• Figure 3: (color online) (a) Normalized to unity at the maximum bin are (solid curves) transverse radial $r_T$ distributions in the gold nucleus for four d+ Au centrality selections and (dashed curve) density weighted longitudinal thickness as a function of $r_T$ ($\Lambda(r_T)$). (b) (points) Unbiased $R_{d\rm{Au}}$ versus $R_{\rm CP}$ for the experimental data and (curves) constraint lines for three geometric dependencies of the nuclear modification.