The results of a study of the annihilation reactions (n) over bar p --> phi pi(+) and (n) over bar p --> omega pi(+) are reported; the data were collected by the OBELIX apparatus, with antineutrons annihilating in flight (momenta from similar to 50 MeV/c to 405 MeV/c). Annihilation frequencies and annihilation cross sections have been deduced, for both channels, as a function of antineutron momentum. From the cross section ratio, a substantial deviation from OZI rule expectations is observed. An (s) over bar s quark content in the nucleon offers a fairly plausible explanation for such an effect. (C) 1999 Elsevier Science B.V. All rights reserved.

The results of a study of the annihilation reactions n̄p → φπ and n̄p → ωπ are reported; the data were collected by the OBELIX apparatus, with antineutrons annihilating in flight (momenta from ∼ 50 MeV/c to 405 MeV/c). Annihilation frequencies and annihilation cross sections have been deduced, for both channels, as a function of antineutron momentum. From the cross section ratio, a substantial deviation from OZI rule expectations is observed. An s̄s quark content in the nucleon offers a fairly plausible explanation for such an effect. c © 1999 Elsevier Science B.V. All rights reserved. PACS: 13.75.-n; 14.40.Cs

The results of a study of the annihilation reactions np → θπ+ and np → ωπ+ are reported; the data were collected by the OBELIX apparatus, with antineutrons annihilating in flight (momenta from ∼ 50 MeV/c to 405 MeV/c). Annihilation frequencies and annihilation cross sections have been deduced, for both channels, as a function of antineutron momentum. From the cross section ratio, a substantial deviation from OZI rule expectations is observed. An ss quark content in the nucleon offers a fairly plausible explanation for such an effect.

The reaction (p) over bar p --> K+K- pi(0) was analysed for antiproton annihilations at rest at three hydrogen target densities. A strong dependence of the (p) over bar p --> phi pi(0) yield on the quantum numbers of the initial state is observed. The branching ratio of the phi pi(0) channel from the S-3(1) initial state is more than 15 times larger than the one from the P-1(1) state. A large apparent violation of the OZI rule for tensor meson production from (p) over bar p-annihilations from the P-waves (1(++) + 2(++)) is observed: R-exp(f(2)'pi(0)/f(2)pi(0)) = (149 +/- 20) . 10(-3), significantly exceeding the OZI-rule prediction R = 16 . 10(-3). (C) 1998 Elsevier Science B.V. All rights reserved.

The spin-parity analysis of the $\mathrm{n\ifmmode \bar{}\else \={}\fi{}}\stackrel{\ensuremath{\rightarrow}}{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ exclusive reaction in flight is presented. The main aim is to study the $({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ invariant mass spectrum in the region around 1500 MeV. The analysis was performed with a Breit-Wigner parametrization for all the resonant states and, for the scalar sector in the mass region below 1.2 GeV, by means of a K-matrix-like treatment. It clearly shows the need for two states, a scalar one ${(0}^{++})$ with mass and width $(1522\ifmmode\pm\else\textpm\fi{}25) \mathrm{MeV}$ and $(108\ifmmode\pm\else\textpm\fi{}33) \mathrm{MeV}$, and a tensorial one ${(2}^{++})$ with mass $(1575\ifmmode\pm\else\textpm\fi{}18) \mathrm{MeV}$ and width $(119\ifmmode\pm\else\textpm\fi{}24) \mathrm{MeV}$, respectively. In addition, the analysis requires the presence of a scalar state at $(1280\ifmmode\pm\else\textpm\fi{}55) \mathrm{MeV}$, $(323\ifmmode\pm\else\textpm\fi{}13) \mathrm{MeV}$ broad, and of a second vectorial one, in addition to the ${\ensuremath{\rho}}^{0}(770)$ signal, with mass and width $(1348\ifmmode\pm\else\textpm\fi{}33) \mathrm{MeV}$ and $(275\ifmmode\pm\else\textpm\fi{}10) \mathrm{MeV}$, respectively.

The study of the I = 1, J(PC) = 0(++) states with the OBELIX detector in the channel (p) over bar p --> K (+/-KsT)-T-0 pi(-/+) at three different target densities is reported. The data show the evidence for an extra scalar state with mass 1.29 +/- 0.01 GeV/c(2) and width 0.080 +/- 0.005 GeV/c(2). (C) 1998 Published by Elsevier Science B.V. All rights reserved.

The reaction p̄p→K+K−π0 was analysed for antiproton annihilations at rest at three hydrogen target densities. A strong dependence of the p̄p→φπ0 yield on the quantum numbers of the initial state is observed. The branching ratio of the φπ0 channel from the 3S1 initial state is more than 15 times larger than the one from the 1P1 state. A large apparent violation of the OZI rule for tensor meson production from p̄p-annihilations from the P-waves (1+++2++) is observed: Rexp(f′2π0/f2π0)=(149±20)·10−3, significantly exceeding the OZI-rule prediction R=16·10−3.

q y 0 The reaction ppTMK K p was analysed for antiproton annihilations at rest at three hydrogen target densities. A 0 strong dependence of the ppTMfp yield on the quantum numbers of the initial state is observed. The branching ratio of the fp 0 channel from the S initial state is more than 15 times larger than the one from the P state. A large apparent 1 1 qq qq Ž . violation of the OZI rule for tensor meson production from pp-annihilations from the P-waves 1 q2 is observed: Ž X 0 0. Ž . y3 y3 R f p rf p s 149"20 P10 , significantly exceeding the OZI-rule prediction Rs16P10 . q 1998 Elsevier exp 2 2 Science B.V. All rights reserved.

The partial wave analysis of the reaction pp → π+π−π0 at rest has been performed for the first time by using high-statistics data sets collected in hydrogen targets at three different densities. The different mixtures of partial waves corresponding to our samples allow a reliable determination of each contribution. This technique is crucial in the identification of the exotic candidate f2(1565) which can be produced by 1S0, 3P1 and 3P2 initial states. The amplitude analysis was performed in the frame of the K-Matrix and P-Vector approach. It requires presence of the exotic candidates f0(1500) and f2(1565) with the following masses and total widths: (1449 ± 20)MeV, (114 ± 30)MeV and (1507 ± 15)MeV, (130 ± 20)MeV respectively. In addition to f0(980), f0(1300) f2(1270) and ϱ(770), a clear evidence of I = 1, JP = 1− signal, which we identify with ϱ(1450), is obtained.

The OBELIX spectrometer, studying at the Low Energy Antiproton Ring (LEAR) of CERN the <(N)over bar N> annihilation, has collected annihilation data with very low momentum (p) over tilde (approximate to 50MeV/c). The results of the spin-parity analysis on the <(p)over bar p> annihilation into four and five pions are briefly described.