2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42647In this talk we review some of the most relevant effects that the mixing with a Q=2/3 quark singlet might give at high energy colliders and K and B factories.LaTeX, 4 pages, 2 PS figures. Presented at the XXIX Biennial Meeting of the Royal Spanish Physics Society (RSEF), published in the proceedingsHigh Energy Physics - Phenomenologytext