  We study single inclusive forward hadron production in high energy
proton-nucleus collisions at next-to-leading order in the Color Glass
Condensate framework. Recent studies have shown that the next-to-leading order
corrections to this process are large and negative at large transverse
momentum, leading to negative cross sections. We propose to overcome this
difficulty by introducing an explicit rapidity factorization scale when
subtracting the rapidity divergence into the evolution of the target.
