2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/230812We review the study the Wandzura-Wilczek relation for the structure function g_2, with a particular attention on the connection with the framework of Transverse Momentum Dependent factorization. We emphasize that the relation is broken by two distinct twist-3 terms. In the light of these findings, we clarify what can be deduced from the available experimental data on g_2, which indicate a breaking of the order 20-40%, and how to individually measure the twist-3 terms.Talk given by Alberto Accardi at "Spin structure at long distances," Jefferson Lab, March 12-13 2009High Energy Physics - Phenomenologytext