2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/43530I overview the physical picture of QCD at low energies that has led to the prediction of a narrow exotic baryon Theta^+ which cannot be made of three quarks. The very narrow width of the Theta^+ and a possible reason why it is seen in low- but not in high-energy experiments are briefly discussed.Invited talks at the meeting of the American Physical Society (Denver) and at the workshop `Continuous Advances in QCD' (Minneapolis). 13 p., 19 figsHigh Energy Physics - Phenomenologytext