2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49309We discuss proton decay induced by dimension--5 operators in supersymmetric models containing extra hypercharge-1/3 color-triplets. We derive a general formula relating dimension-5 operator to the color-triplet mass matrix. We show that certain zeros in the triplet mass-matrix together with some triplet coupling selection rules can lead to elimination of dimension-5 operators. We apply this mechanism to SU(5) and flipped SU(5) theories with extended Higgs sectors.6 pages, uses JHEP.cls, talk given at the Trieste Meeting of the TMR Network on Physics Beyond the Standard Model, 24-27 February 1999, Trieste, Italy (to appear in the proceedings)High Energy Physics - Phenomenologytext