Semileptonic decays of Pseudoscalar mesons in the instant form of relativistic Hamiltonian dynamics

A formalism for describing semileptonic decays of pseudoscalar mesons is developed on the basis of the instant form of relativistic Hamiltonian dynamics. By way of example, this formalism is applied to the decay process $K^ - \to \pi ^0 + \mu ^ - + \bar \nu _\mu $ . Relevant calculations are performed with wave functions that correspond to various models of constituent-quark interactions in mesons. Free parameters that appear in these models are determined from a fit to the root-mean-square radii of the kaons and pions. The results of the calculations agree well with experimental data.