φπ⁰ and φη production in antiproton annihilation at rest in a hydrogen gas target at NTP

Data of antiproton annihilation at rest in a hydrogen gas target at NTP have been collected with the Obelix spectrometer exposed to the beam extracted from the LEAR accelerator of CERN. The reactions pp → φπ⁰ and pp → φη have been studied. The analysis of the angular distribution of the kaons emitted by the φ decay has shown that the reaction pp → φπ⁰ occurs essentially from ³S₁ states with a production rate R_NTP = (2.46 ± 0.23 ± 0.07) × 10^-4, while the rate from ¹P₁ states is compatible with zero. Because of acceptance limitations, ³S₁ and ¹P₁ contributions to the reaction pp → φη could not be resolved and lower and upper limits for the production rate have been measured with the middle value R_NTP = (0.87 ± 0.21) × 10^-4. Also, for the phase-space K⁺K^-η events the production rate R_NTP = (4.67 ± 0.35) × 10^-4 has been measured. The φπ⁰ and φη branching ratios in S- and P-waves (defined in the text) have been estimated in a model dependent way. For the evaluation of the φη rate, a combination of our production rate and of data obtained with a liquid target has been used. The φπ⁰ production rate, compared to our preliminary value for the ωπ⁰ production, confirms the strong violation of the OZI rule observed in other experiments. No violation is apparent in the φη production.