Isospin symmetry breaking in double-pion production in the region of $d^{\ast }(2380)$ and the scalar $\sigma$ meson

M. N. Platonova, V. I. Kukulin

The first attempt is made to provide a quantitative theoretical interpretation of the WASA-at-COSY experimental data on the basic double-pion production reactions $pn\to d{\pi }^0{\pi }^0$…