  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.
