2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/186546We 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.4 pages, 2 figures, a few changes in wording and a typo correction. Version accepted for publication in Phys. Rev. LettHigh Energy Physics - PhenomenologyHigh Energy Physics - ExperimentNuclear Theorytext