S. Bergamaschi

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

Abstract 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 p p → φπ 0 and p p → φη have been studied. The analysis of the angular distribution of the kaons emitted by the φ decay has shown that the reaction p p → φπ 0 occurs essentially from 3 S 1 states with a production rate R NTP = (2.46 ± 0.23 ± 0.07) × 10 −4 , while the rate from 1 P 1 states is compatible with zero. Because of acceptance limitations, 3 S 1 and 1 P 1 contributions to the reaction p p → 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 φπ 0 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 φπ 0 production rate, compared to our preliminary value for the ωπ 0 production, confirms the strong violation of the OZI rule observed in other experiments. No violation is apparent in the φη production.

A preliminary spin-parity analysis on the anti-p.p -> pi+.pi-.eta annihilation at rest

Abstract A preliminary spin-parity analysis performed on the p p → π + π − η annihilation reaction at rest is presented. The data were acquired in Liquid and NTP hydrogen target densities with the OBELIX detector. The obtained results are in agreement with those existing in literature and support the introduction of new resonances.