"$a \to \pi^+\pi^-\pi^0$ (mixing with $\eta$)" of "Search for hadronic decays of feebly-interacting particles at NA62"

Number of expected $a \to \pi^+\pi^-\pi^0$ events for BR = 1 in the plane (mass, width) after full selection, for production in mixing with $\eta$ assuming production coupling $\theta_{\eta} = 1$. Acceptance for particles that reach the FV and decay therein and mass resolution.