Forward azimuthal correlations in 200 GeV p+p and d+Au collisions at   STAR
  Forward particle production and correlation measurements at RHIC can probe low-$x$ gluons. The suppression observed in back-to-back forward $\pi^{0}$+forward $\pi^{0}$ correlations at STAR in central d+Au collisions at STAR is consistent with a prediction of the Color Glass Condensate (CGC) calculation, indicating the gold nucleus probed at such low-$x$ is in a dense gluon state. The forward $\pi^{0}$ + near-forward jet-like cluster azimuthal correlations in 200 GeV p+p and d+Au collisions at STAR are studied, which are sensitive to the intermediate x region between forward+mid-rapidity correlations and forward+forward correlations. Together with the other measurements from STAR, which probe different regions of x, forward+near-forward di-hadron correlations can provide information to understand how sharp is the transition from dilute parton gas to dense gluon state. 
Xuan Li and the STAR Collaboration
nucl-ex hep-ex