Probing Gluons in Nuclei: the Case of ${\eta }^{\prime }$

Abstract

Using the recently proposed $gg-->et{a}^{\prime }$ effective vertex, we investigate the production of ${\eta }^{\prime }$ from gluon fusion in $pA$ collisions. We show that measuring ${\eta }^{\prime }$ production cross-section at moderate $x_{{\eta }^{\prime }}$ yields direct information on the small $x$ gluon distribution function of the nucleus. At RHIC, the smallest accessible $x$ turns out to be $O(10^{-5})$ and at LHC, it is $O(10^{-8})$. Therefore, ${\eta }^{\prime }$ is an excellent probe of the Color Glass Condensate.

Comments: 16 pages, 3 figures