2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/180493We review the theory of spin filtering of stored (anti)protons by multiple passage through the polarized internal target (PIT). Implications for the antiproton polarization buildup in the proposed PAX experiment at FAIR GSI are discussed.4 pages, 1 figure, Presented at the 17th Intl. Spin Physics Symposium, SPIN2006, Kyoto, Japan, October 2-7, 2006High Energy Physics - PhenomenologyNuclear ExperimentNuclear TheoryAccelerator Physicstext