  We confront the theoretical result of single spin asymmetry (SSA) $A_N$ in
forward $pA$ collisions $p^\uparrow A \to hX$ including the gluon saturation
effect with the recent preliminary experimental data from the PHENIX and STAR
collaborations at RHIC. While we find overall reasonable agreement with the
STAR data, our results indicate that the strong nuclear suppression of the
asymmetry $A_N\sim A^{-1/3}$ observed by the PHENIX collaboration cannot be
explained within the present understanding of this problem.
