A. Ferretti

Study of the f(0)(1500)/f(2)(1565) production in the exclusive annihilation (n)over-bar-p ->pi(+)pi(+)pi(-) in flight

The spin-parity analysis of the (n) over bar p --> pi(+)pi(+)pi(-) exclusive reaction in flight is presented. The main aim is to study the (pi(+)pi(-)) 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+/-25) MeV and (108+/-33) MeV, and a tensorial one (2(++)) with mass (1575 +/-18) MeV and width (119+/-24) MeV, respectively. In addition, the analysis requires the presence of a scalar state at (1280+/-55) MeV, (323+/-13) MeV broad, and of a second vectorial one, in addition to the rho(0)(770) signal, with mass and width (1348+/-33) MeV and (275+/-10) MeV, respectively.

Protonium annihilation into KSKL at three different target densities

Abstract The frequency of the protonium annihilation channel p p → K S K L 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( p p → K S K L , LH) = (7.8 ± 0.7 stat ± 0.3 sys ) × 10 −4 , f( p p → K S K L , NTP) = (3.5 ± 0.5 stat ± 0.2 sys ) × 10 −4 and f( p p → K S K L , 5 mbar ) = (1.0 ± 0.3 stat ± 0.1 sys ) × 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.

Study of (n)over-bar-p annihilation in two mesons in the momentum range between 50 to 400 MeV/c with OBELIX

Abstract We measured the in flight annihilation frequencies and cross sections of reactions n p → π + π 0 ,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 n p annihilation dynamics were obtained. The first determination of the D-wave contribution in this momentum range was also obtained.

Study of the anti-p.p -> 2pi+.2pi- annihilation from S states

Abstract The results of the spin-parity analysis of p p → 2π + 2π − annihilations at very low momentum p (≈ 50 MeV/c) are reported. To describe the data the production of the ϱ, f2, a2 and a1 mesons and the presence of the ππ interaction in S-wave (the σ term) in the final state are necessary. The best fit solution requires also the presence of a ϱ′ state of mass and width M = 1.282 ± 0.037, Γ = 0.236 ± 0.036 GeV/c2 and of a heavy pion π(1300) of mass and width M = 1.275 ± 0.015, Γ = 0.218 ± 0.100 GeV/c2. The measured fraction of the annihilation cross section into 2π+2π− is (7.61 ± 0.35) · 10−2.The results of the spin-parity analysis of annihilations at very low momentum (≈ 50 MeV/c) are reported. To describe the data the production of the ϱ, f2, a2 and a1 mesons and the presence of the ππ interaction in S-wave (the σ term) in the final state are necessary. The best fit solution requires also the presence of a ϱ′ state of mass and width M = 1.282 ± 0.037, Γ = 0.236 ± 0.036 GeV/c2 and of a heavy pion π(1300) of mass and width M = 1.275 ± 0.015, Γ = 0.218 ± 0.100 GeV/c2. The measured fraction of the annihilation cross section into 2π+2π− is (7.61 ± 0.35) · 10−2.

n̄p annihilation in flight in two mesons in the momentum range between 50 and 400 MeV/c with OBELIX

Results on np annihilation frequencies into π + π 0 , π + η and K + K s final states in the n momentum range between 50 and 400 MeV/c are presented. Information about np 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 np annihilation cross section data.

Study of the isovector scalar mesons in the channel p̄pK±KS0π‡ at three hydrogen target densities

The study of the I = 1, 0 ++ states with the OBELIX detector in the channel pp → K ±K 0 sπ ∓ at three different target densities is reported. We discuss in particular the results about a o (980) and the evidence of an extra scalar state with mass 1.29 ± 0.01 GeV/c 2 and width 0.080 ± 0.005 GeV/c 2

Dynamical selection rules from pp̄ annihilation at rest in three meson final states

Abstract.The hadronic annihilation branching-ratios in quasi-two-body final states have been obtained from the observation of the reactions

Study of anti-n.p -> phi.pi+ and anti-n.p -> omega.pi+ annihilation reactions in flight

bar p p

Study of thef0(1500)/f2(1565)production in the exclusive annihilationn̄p→π+π+π−in flight

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