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.

We measured the in flight annihilation frequencies and cross sections of reactions np → π+π0,π+η and K+KS in the antineutron momentum range between 50 and 400 MeV/c. The annihilation frequencies of these channels from the different allowed initial states were calculated and some information about the np annihilation dynamics were obtained. The first determination of the D-wave contribution in this momentum range was also obtained.

Results on lip annihilation frequencies into pi(+) pi(0), pi(+)eta and K+KS final states in the (n) over bar momentum range between 50 and 400 MeV/c are presented. Information about <(n)over bar p> annihilation dynamics at low energy have been extracted as well as the first determination of the D-wave contribution to the annihilation in flight below 400 MeV/c. This result is compared with an independent analysis of the <(n)over bar p> annihilation cross section data.

New experimental results on pd annihilation at rest into pions plus a high momentum proton in the final state are discussed. The data sample was collected using the OBELIX spectrometer at the LEAR facility (CERN). The annihilation probabilities, or more precisely the yields (Y) via channels pd → 2π−π+π0p and pd → 3π−2π+π0p with proton momenta p > 400 MeV/c have been measured for the first time: Y = (93.2 ± 1.6) × 10−4 and Y = (52.2 ± 1.4) × 10−4, respectively. The signal in the invariant mass distribution of the pπ+ system in the region of the well-known Δ++(1232)-isobar is clearly seen in reactions pd → 2π−π+p, pd → 2π−π+π0p, pd → 3π−2π+p and pd → 3π−2π+π0p. The upper limit on reaction p(Δ−Δ++) → 2π−π+p in the pd annihilation at rest, which could be interpreted as a manifestation of the ΔΔ component of the deuteron, was found to be Y ≤ 6.5 × 10−5 with a 90% confidence level.

We report in this paper the results of the study of the f(0)(1500)/f(2)(1565) resonances in the in-flight annihilation reaction <(n)over bar p> - 2 pi(+)pi(-), taking into account a possible dependence on the (n) over bar momentum.

The results of the spin-parity analysis of the annihilation reaction <(p)over bar p> --> pi(+)pi(-)pi(0) at rest are presented. For the first time data from liquid, NTP and low pressure hydrogen are fitted simultaneously. This technique allows to disentangle unambiguously the contributions of the different initial atomic states. The results concern the weights of the partial waves, masses and widths of the 0(++), 1(--) and 2(++) resonances produced in the annihilation.

New measurements of the pp total annihilation cross-section at very low momenta (around 50 MeV/c) confirm the previous results obtained by the OBELIX collaboration. The measured values are in general agreement with a scattering length approximation of the annihilation cross-section where the <(p)over bar p> scattering lengths are obtained from measurement of the protonium shifts and widths and which accounts for the Coulomb interaction. Partial annihilation cross-sections and annihilation frequencies for some channels have been measured too. The values of the total and partial cross sections at the lowest (p) over bar momentum show an unexpected behaviour.

Due to a most unfortunate technical mishap, half of the references in the list of references were not printed. Below the full list of references is being reprinted

From the study of the annihilation at rest pp → K±Kmiss0π∓π+π− the production rates of the η(1440) → K±KL0π∓ were obtained for three different hydrogen target densities: liquid, gaseous at NTP and at low pressure (5 mbar). The rate values are: fη(1440) (LH) = (6.0±0.5) · 10−4, fη(1440) (NTP) = (2.9±0.4) · 10−4 and fη(1440) (5mbar) = (1.0±0.2) · 10−4. From these results, the density dependence of the annihilation fraction from the 1S0 protonium level can be extracted directly.

The results of a spin-parity analysis of (n) over bar p annihilation in the channels with 3 and 5 charged pions are presented. In the former case, the analysis suggests the existence of two resonances with quantum numbers 0(++) and 2(++) around 1500-1550 MeV/c(2); in the latter case, the presence of a broad resonance at about 1350 MeV/c(2) decaying dominantly into rho rho is confirmed, but a great amount of rho sigma (1(-)) nonresonant background is required.

The results of the preliminary analysis of 4840 (K (K) over bar pi)pi pi events, from a data sample of 24 million (p) over bar p annihilations at rest in a gaseous hydrogen target at NTP, collected with the OBELIX spectrometer at LEAR (CERN), are presented. The presence of two pseudoscalar states in the region around 140 MeV/c(2), already seen, for the first time, in (p) over bar p annihilations at rest from analysis of a data set taken with a liquid hydrogen target, is confirmed, The lighter mass resonance decays mainly into K (K) over bar pi, while the higher mass 0(-+) state decays only into K*(K) over bar. A sizable fraction of direct K*(K) over bar production, from the initial P-wave protonium state (about twice the value in liquid hydrogen), is observed, as expected. No significant evidence for an axial vector emerges from this preliminary analysis

The results of the preliminary analysis of 4840 (K (K) over bar pi)pi pi events, from a data sample of 24 million (p) over bar p annihilations at rest in a gaseous hydrogen target at NTP, collected with the OBELIX spectrometer at LEAR (CERN), are presented. The presence of two pseudoscalar states in the region around 140 MeV/c(2), already seen, for the first time, in (p) over bar p annihilations at rest from analysis of a data set taken with a liquid hydrogen target, is confirmed, The lighter mass resonance decays mainly into K (K) over bar pi, while the higher mass 0(-+) state decays only into K*(K) over bar. A sizable fraction of direct K*(K) over bar production, from the initial P-wave protonium state (about twice the value in liquid hydrogen), is observed, as expected. No significant evidence for an axial vector emerges from this preliminary analysis.

The frequency of the protonium annihilation channel pp → KSKL has been measured at three different target densities: liquid hydrogen (LH), gaseous hydrogen at NTP conditions and gaseous hydrogen at low pressure (5 mbar). The obtained results are: f(pp → KSKL, LH) = (7.8 ± 0.7stat ± 0.3sys) × 10−4, f(pp → KSKL, NTP) = (3.5 ± 0.5stat ± 0.2sys) × 10−4 and f(pp → KSKL, 5 mbar) = (1.0 ± 0.3stat ± 0.1sys) × 10−4. Since the KSKL final stat and be originated only from the 3S1 initial state, these values give direct information on the scaling of the protonium spin-triplet S-wave annihilation probability with the density.

phi pi(+)pi(-) production in (p) over bar p annihilation at rest in liquid and gaseous hydrogen at low pressure (5 mbar) is studied in the OBELIX experiment at LEAR (CERN). It is found that this reaction is dominated by the annihilation from the (p) over bar p spin-triplet initial states.

New results concerning the detection of (p) over bar d Pontecorvo reactions at rest with hidden and open strangeness in the final state are presented. A very selective 2-prong dedicated trigger has been used to collect a sample of about 8.5 x 10(6) annihilations. Evidence of the reaction (p) over bar d --> phi n is shown with a branching ratio of [5.3 +/- 0.6(stat.) +/- 0.3(syst.)] x 10(-6). Moreover, the reactions (p) over bar d --> Lambda K* and (p) over bar d --> Lambda K-L(0) have been identified through the reconstruction of the decay Lambda(0) --> p pi(-). The preliminary result for the branching ratio is Br((p) over bar d --> Lambda(0)K(L)(0)) = [5 +/- 1(stat.)+/- 2(syst)] x 10(-7).