Results are presented for a measurement for the production of the antihydrogen atom , the simplest atomic bound state of antimatter. A method has been used by the PS210 collaboration at LEAR which assumes that the production of is predominantly mediated by the e+e−-pair creation via the two-photon mechanism in the antiproton-nucleus interaction. Neutral atoms are identified by a unique sequence of characteristics. In principle is well suited for investigations of fundamental CPT violation studies under different forces, however, in our investigations we concentrate on the production of this antimatter object, since so far it has never been observed before. The production of 11 antihydrogen atoms is reported including possibly 2±1 background signals, the observed yield agrees with theoretical predictions

Abstract. The production of the Λ and Σ 0 hyperons has been measured via the pp → pK + Λ/Σ 0 reaction at the internal COSY-11 facility in the excess energy range between 14 and 60 MeV. The transition of the Λ/Σ 0 cross section ratio from about 28 at Q ≤ 13 M eV to the high energy level of about 2.5 is covered by the data showing a strong decrease of the ratio between 10 and 20 MeV excess energy. Effects from the final state interactions in the p − Σ 0 channel seems to be much smaller compared to the p − Λ one. Estimates of the effective range parameters are given for the N Λ and the N Σ systems.

Abstract:The energy dependence of the total cross section for the pp −→ pK + Λ reaction was measured in the threshold region covering the excess energy range up to 7 MeV.Existing model calculations describe the slope of the measured cross sections well, but are too low by a factor of two to three in rate.The data were used for a precise determination of the beam momentum of the COSY-synchrotron.

The production of η mesons has been measured in the proton-proton interaction close to the reaction threshold using the COSY-11 internal facility at the cooler synchrotron COSY. Total cross sections were determined for eight different excess energies (ǫ) in the range from ǫ = 0.5 MeV to ǫ = 5.4 MeV.The energy dependence of the total cross section is well described by the available phase-space volume weighted by FSI factors for the proton-proton and proton-η pairs.

The first measurement of the cross section of the quasifree pn→pn reaction has been carried out at the CELSIUS storage ring using a deuterium internal cluster jet target. The energy dependence of the cross section is extracted using a fixed incident proton energy of T p ϭ1350 MeV and exploiting the Fermi momentum of the struck neutron. The data cover a range of center-of-mass excess energies from 16 to 109 MeV. The shape of the excitation function is broadly similar to that of the pp→pp reaction, though with a cross section about a factor of 6.5 larger. ͓S0556-2813͑98͒02811-8͔