  In the framework of Color Glass Condensate (CGC) effective field theory
(EFT), we calculate two-gluon rapidity correlations in the leading and
sub-leading orders of $p_\perp/Q_s$. In the leading order, both short- and
long-range rapidity correlations are enhanced. In contrast, the contribution of
sub-leading order is mainly short range quantum correlations. It is much
smaller than that of the leading one, but is not negligible. Transverse
momentum dependence of rapidity correlation shows that the leading order is
sensitive to the saturation momentum of two incident particles, but the
sub-leading one is not.
