On the Form Factors of the $D_{s}^{+}\to ϕμ^{+}ν_μ decay

F. Hussain, A. N. Ivanov, N. I. Troitskaya

We apply the infinite mass effective theory, when a heavy quark mass tends to infinity, and Chiral perturbation theory at the quark level, based on the extended Nambu -- Jona -- La…