Neutral Pion Suppression at Forward Rapidities in d+Au Collisions at STAR

TL;DR

This paper reports measurements of neutral pion yields at forward rapidities in p+p and d+Au collisions at 200 GeV, showing suppression consistent with gluon density reduction models in nuclei.

Contribution

It provides experimental data on pi0 production at forward rapidities and compares results with perturbative QCD and Color Glass Condensate models.

Findings

p+p yields agree with perturbative QCD

d+Au yields align with Color Glass Condensate models

nuclear modification factor indicates gluon suppression in nuclei

Abstract

Measurements of the inclusive yields of pi0 mesons in p+p and d+Au collisions at center of mass energy sqrt(s_NN)=200 GeV and pseudorapidity <eta>=4.00 (d beam direction) are reported. The yield for p+p collisions is in general agreement with perturbative QCD calculations. The d+Au yield is in agreement with a calculation which models the Au nucleus as a Color Glass Condensate for forward particle production. The nuclear modification factor derived from the inclusive yields is qualitatively consistent with models which suppress the gluon density in nuclei.