Polarized Gluon Distribution Function from $\eta'$ Production
  Using the recently proposed $gg\eta'$ effective vertex, we investigate the production of $\eta'$ from gluon fusion in polarized pp collisions. We show that by measuring $A_{LL}$ in $\eta'$ production, one can extract the polarized gluon distribution $\Delta G(x,Q^2)$ at $Q^2 \sim 1 \GeV^2$ and in a wide range of x. 
Sangyong Jeon and Jamal Jalilian-Marian