Nuclear Modification Factor in d+Au Collisions: Onset of Suppression in the Color Glass Condensate

Abstract

We perform a quantitative analysis of the nuclear modification factor in deuteron--gold collisions R(dAu) within the Color Glass Condensate approach, and compare our results with the recent data from RHIC experiments. Our model leads to Cronin enhancement at mid-rapidity, while at forward rapidities it predicts strong suppression of R(dAu) at all pT due to low-x evolution. We demonstrate that our results are consistent with the data for dAu charged hadron spectra, R(dAu) and R(CP) recently reported for rapidities in the interval eta=0--3.2 by the BRAHMS experiment at RHIC. We also make a prediction for R(pA) at mid-rapidity in pA collisions at the LHC.

Figures (4)

• Figure 1: Charged particle spectra in Deuteron-Gold collisions at $\sqrt{s}=200$ GeV at RHIC. For the plots with $\eta=0,1$ the solid line corresponds to $(h^-+h^+)/2$ contribution calculated in the isospin-independent approximation for the fragmentation functions with $\kappa=0$, while the dashed line gives the same $(h^-+h^+)/2$ contribution for $\kappa=1$ GeV. In the plots for $\eta=2.2,3.2$ the solid line denotes the $h^-$ contribution calculated in the constituent quark approximation with $\kappa=0$, the dashed line gives the same $h^-$ contribution for $\kappa=1$ GeV, while the dotted line at $\eta=2.2,3.2$ gives the $(h^++h^-)/2$ isospin-independent contribution calculated for $\kappa=0$. Data is from BRAHMSdata.
• Figure 2: Nuclear modification factor $R_{dAu}$ of charged particles for different rapidities. In the top two figures, corresponding to $\eta=0,1$, the solid line corresponds to $(h^-+h^+)/2$ contribution calculated with $\kappa=0$ in the isospin-independent approximation, while the dashed line gives the same $(h^-+h^+)/2$ contribution but with $\kappa=1$ GeV. In the lower two plots, corresponding to $\eta=2.2,3.2$, the solid line gives the $h^-$ contribution calculated in the constituent quark model with $\kappa=0$, the dashed line gives the same $h^-$ contribution for $\kappa=1$ GeV, while the dotted line at $\eta=2.2,3.2$ gives the $(h^++h^-)/2$ contribution with $\kappa=0$. Data is from BRAHMSdata.
• Figure 3: Nuclear modification factor $R_{CP}$ of charged particles $(h^++h^-)/2$ calculated in the isospin-independent approximation for rapidities $\eta=0,1$ and $R_{CP}$ of negatively charged particles $h^-$ calculated in the constituent-quark model for $\eta=2.2,3.2$ plotted for $\kappa=0$. Data is from BRAHMSdata. Full and open dots, described by the solid and dashed lines correspondingly, give the ratio of particle yields in 0-20$\%$ and 30-50$\%$ centrality events correspondingly divided by the yields from 60-80$\%$ centrality events scaled by the mean number of binary collisions BRAHMSdata.
• Figure 4: Nuclear modification factor $R^{pA}$ of charged particles $(h^++h^-)/2$ at LHC energies $\sqrt{s}=5500$ GeV at mid-rapidity $\eta=0$ (dashed line) versus $R^{dAu}$ of $(h^++h^-)/2$ for RHIC energies $\sqrt{s}=200$ GeV at $\eta=3.2$ (solid line) plotted for $\kappa=0$.