Two-particle correlations at forward rapidity in STAR

During the 2008 run RHIC provided high luminosity in both p + p and d + Au collisions at . Electromagnetic calorimeter acceptance in STAR was enhanced by the new Forward Meson Spectrometer (FMS), and is now almost continuous over −1<η<4 and the full azimuth. This large acceptance provides sensitivity to the gluon density in the nucleus down to x≈10−3, as expected for 2→2 parton scattering. Measurements of the azimuthal correlation between a forward π0 and an associated particle at large rapidity are sensitive to the low-x gluon density. Data exhibit the qualitative features expected from gluon saturation. A comparison to calculations using the Color Glass Condensate (CGC) model is presented.