Interference phenomena in the decay Ds+ → ηπ0 π+ induced by the a00(980) - f0(980) mixing

Using the data on the decay D-s(+) -> f(0)(980)pi(+) -> K+ K- pi(+), we estimate the amplitude of the process D-s(+) -> [f(0)(980) -> (K+ K- + K-0 K-0) -> a(0)(0(980))]pi(+) -> eta pi(0)pi(+), caused by the mixing of a(0)(0)(980) and f(0)(980) resonances that breaks the isotopic invariance due to the K+ and K-0 meson mass difference. Effects of the interference of this amplitude with the amplitudes of the main mechanisms responsible for the decay D-s(+) -> eta pi(0)pi(+) are analyzed. As such mechanisms, we examine the transition D-s(+) -> eta rho(+) -> eta pi(0)pi(+) , which is observed in experiment, and the possible transition D-s(+) -> (a(0)(0)(980)pi(+) + a(0)(+)(980)pi(0)) -> eta pi(0)pi(+) , It is shown that the rapidly varying phase of the a(0)(0)(980) - f(0)(980) transition amplitude strongly influences the interference curves.