2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/180393Establishing the twist-3 formalsim for the single transverse spin asymmetry, we present a complete single-spin-dependent cross section for SIDIS, $ep^\uparrow\to eπX$, associated with the twist-3 distribution for the transversely polarized nucleon. We emphasize that the consistency condition from the Ward identities for color gauge invariance is crucial to prove factorization property of the cross section.Talk presented at SPIN 2006. 4 pages. Typos are correctedHigh Energy Physics - Phenomenologytext