2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47851The partial width of the decay D^*+_s -> D^+_s pi^0 going through the violation of isotopical symmetry is computed with respect to the partial width of the radiative decay D^*+_s -> D^+_s gamma in the effective quark model with chiral U(3)xU(3) symmetry incorporating Heavy quark effective theory (HQET) and Chiral perturbation theory at the quark level (CHPT)_q. We investigate a sensitivity of the ratio of the partial widths R_0 to current s-quark mass corrections and find a strong dependence.7 pages, Latex, no figuresHigh Energy Physics - Phenomenologytext