Description of the processes $e^+ e^- \to \pi^+ \pi^-$ and $\tau^- \to \pi^- \pi^0 \nu_\tau$ in the NJL model with value of the vector coupling constant $ g_{\rho} = 6$

It is shown that the processes $e^+ e^- \to \pi^+ \pi^-$ and $\tau^- \to \pi^- \pi^0 \nu_\tau$ can be described in a unified approach in satisfactory agreement with experiment using the vector coupling constant $g_{\rho} = 6$. In this case, in addition to quark loops, it is also necessary to take into account meson loops corresponding to the next order in $1/N_c$. These loops must be taken into account when describing the $\gamma (W) \to \rho$ transition, as well as in interaction of mesons in the final state.

M.K. Volkov, A.A. Pivovarov, K. Nurlan · 2024