Proton-proton and proton-eta invariant mass distributions and the total cross section for the pp to pp eta reaction have been determined near the threshold at an excess energy of Q=10 MeV. The experiment has been conducted using the COSY-11 detector setup and the cooler synchrotron COSY. The determined invariant mass spectra reveal significant enhancements in the region of low proton-proton relative momenta, similarly as observed previously at higher excess energies of Q=15.5 MeV and Q= 40MeV.
Total cross section determined from the integral of the invariant mass distribution.
Distribution of the square of the invariant mass of the proton-proton system.
Distribution of the square of the invariant mass of the proton-eta system.
The ratio of the total exclusive production cross sections for $\eta\prime$ and $\eta$ mesons has been measured in the $pp$ reaction at $p_{beam}=3.67$ GeV/c. The observed $\eta\prime/\eta$ ratio is $(0.83\pm{0.11}^{+0.23}_{-0.18})\times 10^{-2}$ from which the exclusive $\eta\prime$ meson production cross section is determined to be $(1.12\pm{0.15}^{+0.42}_{-0.31})\mu b$. Differential cross section distributions have been measured. Their shape is consistent with isotropic $\eta\prime$ meson production.
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No description provided.
Only statistial errors.
The total cross section of the pp -> pp eta' reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding eta production, in good agreement with the predictions of a one-pion-exchange model.
Axis error includes +- 10/10 contribution (Overall normalization error already included).
Axis error includes +- 10/10 contribution (Overall normalization error already included).
The production of eta 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 in the range from 0.5 MeV to 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-eta pairs.
The total cross sections as a function of beam momentum and excess energy with statistical errors. The uncertainty on the beam momentum and excess energy are +- 0.00080 GeV and +- 0.28 MeV respectively.
The pp → ppη reaction has been measured at six energies close to threshold, from 1258 MeV to 1352 MeV, using an internal cluster gas jet target in the CELSIUS storage ring. The η is detected through its decay photons, in an array of CsI detectors, and the forward-going protons are detected in a plastic scintillator spectrometer. A complete event reconstruction is obtained at the higher energies in the measured interval. The new data, together with earlier data, give an accurate determination of the energy dependence close to threshold. The influence of the η-proton FSI is seen in the total cross section data as well as in a Dalitz plot of the η-p invariant mass distributions.
No description provided.
The total cross section of the pp→ pp η reaction has been measured at incident proton energies of 1.265, 1.3, 1.4 and 1.5 GeV by detecting the two photons from the η decay in the PINOT spectrometer. The data are compared with other near-threshold measurements and with the predictions of existing theoretical calculations.
Value given at 1263 MeV assumes energy 2 MeV lower than nominal value. This uncertainty only affects this lowest energy point.
The pp→ppη reaction is studied at energies near the η production threshold. The total cross sections at nominal machine energies of 1260, 1265, and 1300 MeV are 90±15, 790±120, and 3460±690 nb, respectively. None of the existing perturbative model calculations reproduces the energy dependence, which deviates strongly from phase space. This suggests that the cross section is enhanced in the near vicinity of the production threshold by a large η−pp scattering length.
No description provided.
Approximately 21 000 four-prong pp interactions at 13.1 GeV/ c have been studied using the CERN 2m hydrogen bubble chamber. The following reactions have been analyzed pp→ppπ + π − (1) pp→ppπ + π − π 0 (2) pp→ppπ + π + π − (3) The Δ-production is the dominant feature. We also observed the pππ decay of the N ∗ (1470) and N ∗ (1690). The ϱis weakly produced in the three reactions. The η and the α are observed in the reaction (2) and the presence of a ω isobar is discussed. Then the kinematical characteristics of the final particles are described.
NORMALIZED TO A TOTAL CROSS SECTION OF 39.6 +- 0.2 MB.
RESONANCE PRODUCTION ESTIMATED BY CUTS WITH MONTE-CARLO AND HAND-DRAWN PHASE SPACE DISTRIBUTIONS.
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