  We extend previous results (arXiv:0804.2630 [hep-ph]) on factorization in
high-energy nucleus-nucleus collisions by computing the inclusive multigluon
spectrum to next-to-leading order. The factorization formula is strictly valid
for multigluon emission in a slice of rapidity of width \Delta Y< 1/\alpha_s.
Our results show that often neglected disconnected graphs dominate the
inclusive multigluon spectrum and are essential to prove factorization for this
quantity. These results provide a dynamical framework for the Glasma flux tube
picture of the striking "ridge"-like correlation seen in heavy ion collisions.
