  We study the production of heavy quarkonium in association with an additional
heavy pair. We argue that important contributions may come from phase space
regions where three heavy fermions are separated by relative velocities much
lower than the speed of light, and to which standard effective field theories
do not apply. In this region, infrared sensitive color exchange is specific to
the presence of the unpaired (anti)quark. This effect vanishes as the motion of
the additional particle becomes relativistic with respect to the pair, and is
completely absent for massless quarks and gluons in the final state.
