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Cold nuclear matter physics at forward rapidities from d+Au collisions in PHENIX

We present measurements by the PHENIX experiment at RHIC of di-hadron pair production in \dAu collisions where the particles in the pair are varied across a wide range of pseudorapidity, out to $η= 3.8$. With di-hadrons, varying the $p_T$ and rapidity of the particles in the di-hadron pair allows studying any effects as a function of partonic $x$ in the nucleus. These di-hadron measurements might probe down to parton momentum fractions x $\sim$ $10^{-3}$ in the gold nucleus, where the interesting possibility of observing gluon saturation effects at RHIC is the greatest. Our measurements show that the correlated yield of back-to-back pairs in \dAu collisions is suppressed by up to an order of magnitude relative to \pp collisions, and increases with greater nuclear path thickness and with a selection for lower x in the Au nucleus.