On the $D^{*+}_{s} \to D^{+}_{s} \pi^{0}$ decay in the Effective quark model with chiral $U(3) x U(3)$ symmetry

The 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 predict the ratio R^{th}_0 = \Gamma(D^{*+}_s -> D^+_s \pi^0)/\Gamma(D^{*+}_s -> D^+_s 0.062^{+0.020}_{-0.018}\pm 0.022.