We report on a measurement of the branching ratio of the rare decay ω→ηγ relative to the well known decay ω→π0γ. The ω’s are produced in pp→ηω and pp→π0ω. Eigenstate mixing and interference effects of the ω and ρ are taken into account, as well as coherent interference with the background. We find evidence for the non-resonant annihilation channel BR(pp→ηηγ) = (3.5± 1.3)×10−5 and limit the value of BR(ω→ηγ) to the range of (0.7 to 5.5)×10−4 depending on the degree of coherence with the background. 13.20.Jf Decays of other mesons Typeset using REVTEX 3

A partial-wave analysis of the reaction p $($) over bar$$ p-->pi(0) pi(0) pi(0) has been performed using a high-quality high-statistics data set of 712 000 events. In addition to the f(0)(975) and f(0)(1300), the scalar resonance with mass m = (1500 +/- 15) MeV and width Gamma = (120 +/- 25) MeV is necessary to describe the data.

The values of the pion nucleon (\ensuremath{\pi}N) \ensuremath{\sigma} term, as determined, on the one hand, from experimental pion nucleon scattering by means of dispersion relations and, on the other hand, from baryon masses by means of chiral perturbation theory, differ by 10 to 15 MeV. The origin of this discrepancy is not yet understood. If the difference between the two values is attributed to the scalar current of strange sea quark pairs within the proton, the contribution to the proton mass would be of the order of 120 MeV. The discrepancy may hint at either theoretical deficiencies or an inadequate \ensuremath{\pi}N database. In order to provide reliable experimental data we have measured angular distributions of elastic pion proton scattering at pion energies ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=32.2 and 44.6 MeV using the magnet spectrometer LEPS located at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland. From the data covering the region of the Coulomb nuclear interference, the real parts of the isospin-even forward scattering amplitude Re${\mathit{D}}^{+}$(t=0), have been determined as a function of energy. The results have been compared with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, revealing discrepancies most pronounced for the ${\mathrm{\ensuremath{\pi}}}^{+}$p data. The experimentally determined values for Re${\mathit{D}}^{+}$(t=0), however, support the KH80 prediction (which is based on \ensuremath{\pi}N data available in 1979).

We report on measurements of the differential ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$p cross section at pion energies ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=32.7, 45.1, and 68.6 MeV. The measurements, covering the angular range 25\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$\ensuremath{\le}123\ifmmode^\circ\else\textdegree\fi{}, have been carried out at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland, employing the magnet spectrometer LEPS. The absolute normalization of the ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$p cross sections have been achieved by relating them to the electromagnetic cross sections of ${\mathrm{\ensuremath{\mu}}}^{\ifmmode\pm\else\textpm\fi{}\mathrm{}12}$C scattering. The results are in agreement with those of our preceding measurements at ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=32.2 and 45.1 MeV insofar as they overlap with the region of the Coulomb nuclear interference investigated there. A comparison with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, which has formed the basis for the determination of the ``experimental'' \ensuremath{\sigma} term, reveals considerable deviations. These are most pronounced for the ${\mathrm{\ensuremath{\pi}}}^{+}$p cross sections at ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=32.7 and 45.1 MeV. Single energy partial wave fits result in S-wave contributions, which are about 1\ifmmode^\circ\else\textdegree\fi{} lower in magnitude then those specified by the KH80 solution. The data at 68.6 MeV are in good agreement with the phase shift analysis.

The values of the pion nucleon (\ensuremath{\pi}N) \ensuremath{\sigma} term, as determined, on the one hand, from experimental pion nucleon scattering by means of dispersion relations and, on the other hand, from baryon masses by means of chiral perturbation theory, differ by 10 to 15 MeV. The origin of this discrepancy is not yet understood. If the difference between the two values is attributed to the scalar current of strange sea quark pairs within the proton, the contribution to the proton mass would be of the order of 120 MeV. The discrepancy may hint at either theoretical deficiencies or an inadequate \ensuremath{\pi}N database. In order to provide reliable experimental data we have measured angular distributions of elastic pion proton scattering at pion energies ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=32.2 and 44.6 MeV using the magnet spectrometer LEPS located at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland. From the data covering the region of the Coulomb nuclear interference, the real parts of the isospin-even forward scattering amplitude Re${\mathit{D}}^{+}$(t=0), have been determined as a function of energy. The results have been compared with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, revealing discrepancies most pronounced for the ${\mathrm{\ensuremath{\pi}}}^{+}$p data. The experimentally determined values for Re${\mathit{D}}^{+}$(t=0), however, support the KH80 prediction (which is based on \ensuremath{\pi}N data available in 1979).

The existence of exotic states that do not fit into the picture of qqBAR-mesons is still an unanswered question of QCD. Proton-antiproton annihilation at higher momenta might be a promising source in the search for such states. This report shows the first results obtained using the Crystal Barrel detector system at LEAR (CERN) at an antiproton beam momentum of 1940 MeV/c.

We have studied pp annihilations at rest in liquid hydrogen into the final state ωηπ0 where ω decays to π0γ. This reaction is dominated by the production of α0(980) and contributions from a2(1320) and b10(1235). Upper limits for the production of an axial vector h′1(1380) meson and vector mesons ω(1390), ω(1600), and φ(1680) decaying to ωη are given. The branching ratio of pp annihilation into ωηπ0 was determined to be (0.68±0.01±0.05)%.