2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/229207A model-independent analysis of collinear three-parton correlation functions for fragmentation is performed. By investigating their support properties it is shown, in particular, that the so-called partonic pole matrix elements vanish. This sheds new light on the understanding of transverse single spin asymmetries in various hard semi-inclusive reactions. Moreover, it gives additional strong evidence for the universality of transverse-momentum-dependent fragmentation functions.4 pages, 2 figures; minor changes, matches journal versionHigh Energy Physics - PhenomenologyHigh Energy Physics - Experimenttext