The reactions π−p→ n+(X0→total) and π−p→ n+(X0→neutrals) have been studied at 1.6 GeV/c with the Bologna-CERN neutron missing-mass spectrometer. Both reactions have been detected without the use of visual techniques. The results are: σ(X0→total)=(108±14) μb and σ(X0→neutrals)=(20.0±3.5) μb, giving a branching ratio Γ(X0→neutrals)/Γ(X0→total)=(18.5±2.2)%. The branching ratio for other possible, so far undetected, neutral decay modes of the X0 turns out to be (2.4±1.9)%.
No description provided.
Final states with a Ξ− hyperon have been studied in 5.5-GeV/c K−p interactions. Center-of-mass production angular distributions for the Ξ− have a peak in the beam direction, while those for the K+ or K0 meson peak in the opposite direction. Approximately half of the observed events involve the Ξ*(1530) or K*(890) resonances. The four- and five-body final states show production of the Ξ*(1930) in the Ξ−π+,0 mass spectrum and a narrow peak at 2295 MeV in the Ξ−π+π− mass spectrum. The mass of the Ξ− hyperon is 1321.9±0.5 MeV as determined from 195 Ξ− decays with a visible Λ decay, assuming a Λ-hyperon mass of 1115.58 MeV.
No description provided.
Approximately 60 000 events have been collected in a spark chamber experiment at the CERN Proton Synchrotron which studied elastic diffraction scattering of π--p and p-p at incident momenta of 8.5, 12.4 and 18.4 GeV/c and of π+-p at 8.5 and 12.4 GeV/c. Magnetic analysis of the incoming and diffraction scattered particle, together with measurement of all angles, permitted each event to be determined as elastic subject to three constraints, so that the inelastic background was rejected with. high efficiency, even at the larger momentum, transfers. Much of the data have been processed by the CERN Automatic Flying-Spot DigitizerHPD. A detailed description of the experimental technique and of the methods of analysis is given. The results, together with data from lower energies, confirm the remarkable energy-independence of the shape of the pion-proton diffraction scattering peak up to |t| = 1.5 (GeV/c)2, wheret is the square of the four-momentum transfer, over a range of pion energies from 2 to 18 GeV. Proton-proton scattering does however appear to show a shrinking diffraction peak. In general, the data agree with other experiments using both counter and bubble chamber techniques, but some differences do appear. During the experiment, data were taken which set an upper limit of 2·102 μb/(GeV/c)2 on the differential elastic cross-section dσ/dt over a range of |t| from 20.9 to 23.4 (GeV/c)2 at 13.4 GeV/c incident pion momentum.
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