Protonium annihilation into ${\pi }^0{\pi }^0$ at rest in a liquid hydrogen target

The annihilation frequency of the reaction $\overline{p}\overrightarrow{p}{\pi }^0{\pi }^0$ at rest in liquid hydrogen has been measured by the Obelix experiment by using different apparatus configurations and trigger conditions. The value obtained is $f({\pi }^0{\pi }^0,$ $\mathrm{LH})=(2.8\mathrm{}\pm {0.1}_{\mathrm{stat}}\pm {0.4}_{\mathrm{syst}})\times {10}^{-4}.$ With the same data samples, the ${\pi }^0\eta$ annihilation frequency has been determined to be $f({\pi }^0\eta ,$ $\mathrm{LH})=(0.9\mathrm{}\pm {0.2}_{\mathrm{stat}}\pm {0.1}_{\mathrm{syst}})\times {10}^{-4}.$ The results are discussed within the frame of the present experimental situation.