It is well known that gluon distributions dominate the small-x regime of QCD where partons carry a small fraction of the momentum of the parent hadron. The large growth of these gluon distributions makes increasingly important to consider processes with multiple interactions in which the transverse momentum of the incoming partons become relevant. Through a systematic study of two particle production processes, it is possible to establish an effective transverse momentum factorization for asymmetric collisions of a dilute probe on a dense target. Even though different gluon distributions are needed to describe different processes, it is shown that all of them can be obtained as convolution of two basic building blocks.

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