Structure Dependence in $π\to \bf\ellν, π to \ellνγ$ and $π^0\ to γγ$ Decays

Abstract

The amplitudes of $π$-meson decays are calculated in a relativistic nonperturbative quark model which assumes that mesons are made of a quark antiquark pair and of a scalar neutral component representing the contribution of the nonelementary fluctuations of the quark gluonic field. The experimental data can be fitted in a satisfactory manner using current quark masses $m_u\approx1.5\ MeV, m_d\approx9\ MeV$.