Measurements of the reaction p̄p→φη of antiproton annihilation at rest at three hydrogen target densities

Abstract The p p annihilation at rest into the φη final state was measured for three different target densities: liquid hydrogen, gaseous hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in the liquid hydrogen target is smaller than in the low-pressure gas target. The branching ratios of the φη channel were calculated on the basis of simultaneous analysis of the three data samples. The branching ratio for annihilation into φη from the 3 S 1 protonium state turns out to be about ten times smaller as compared to the one from the 1 P 1 state.