Annihilations of Antiprotons at Rest in Hydrogen. V. Multipion Annihilations

Approximately 45 000 pionic annihilations of stopped antiprotons in hydrogen have been measured and analyzed. The relative annihilation rates into the various multipion final states are presented. The experimental distributions of the invariant masses of all the possible pion combinations have been obtained. Strong production of the $\rho$, $\omega$, and $\eta$ meson has been observed, and their production rates have been established. The rates for simultaneous production of ${\rho }^0{\rho }^0$, ${\rho }^0{\omega }^0$, and ${\rho }^0{\eta }^0$ are discussed.