Phenomenological description of the $D^*_{s0}(2317)\to D_s\pi^0$ decay

For coupled channels $D^0K^+$, $D^+K^0$, $D_s^+\eta$, and $D_s^+\pi^0$, the $S$-wave scattering amplitudes are constructed taking into account the mixing of the isoscalar resonance $D^*_{s0}(2317)^+$ with nonresonance amplitudes with isospin $I=1$. The phenomenological approach we use allows us to quite simply clear up the general structure of the $D^*_{s0}(2317)^+\to D_s^+\pi^0$ decay amplitude violating isospin. We show that the phase of this amplitude coincides with the phase of the nonresonanct $D_s^+\pi^0$ scattering amplitude in agreement with the Watson theorem. Its modulus squared, as it should be, determines the width of the resonance peak in the $D_s^+\pi^0$ channel. Taking into account the $\pi^0-\eta$ mixing in internal lines up to the second order inclusively ensures that the unitarity condition is fulfilled. The presented analysis complements the description of the $D^*_{s0}(2317 )^+\to D_s^+\pi^0$ decay based on the coupled channel unitarized chiral perturbation theory. The numerical estimates obtained by us for the $D^*_{s0}(2317)^+\to D_s^+\pi^0$ decay width do not contradict those available in the literature.