The differential cross-sections for the annihilation processes p p→π − π + and p p→K − K + have been measured at an incident laboratory momentum at 5 GeV/ c . Strong backward and forward peaks are observed in the π + π − differential cross-sections while the K + K − cross-section is shown to have a peak only for K − going forward. The annihilation cross-sections are compared with the cross-sections for the crossed channel backward processes π ± p→p π ± and K ± p→pK ± .
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Antiproton-proton elastic scattering has been measured at 5 GeV/c. A total of 30 000 events were observed in the angular range 17° < θ cm < 136°, corresponding to 0.3 < − t < 7.7 (GeV/ c 2 ). In addition to the known dip at − t = 0.5 ( GeV / c ) 2 , we observe a structure at about − t = 2 (GeV/ c ) 2 and a backward peak with a slope4.1 ± 0.6 (GeV/ c ) 2 . The extrapolated differential cross-section at u = 0 is 1.3 ± 0.8 μ b/(GeV/ c ) 2 .
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The differential cross-section for 5 GeV/ cπ + p and π − p elastic scattering have been measured in the c.m. angular region 27° < θ cm < 130° corresponding to 0.5 < | t | < 7.8 (GeV/ c ) 2 . Dips are observed in both reactions at − t = 2.8 and 4.8 (GeV/ c ) 2 where the cross-sections are approximately 0.1 μ b/(GeV/ c ) 2 .
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We have investigated the above processes at the CERN Intersecting Storage Rings (ISR). Results show a marked change of the slope parameter b ( t , s ) = (d/d t ) ln (d σ /d t ) around − t ≈ 0.10 GeV 2 . The s − and t − dependence of b ( t , s ) have been observed over the interval 460 GeV 2 < s < 2900 GeV 2 and 0.02 GeV 2 < t < 0.40 GeV 2 .
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From 2728 events of 205-GeV pp interactions found in 15 000 pictures taken with the 30-in. hydrogen bubble chamber at the National Accelerator Laboratory, a total cross section of 39.5±1.1 mb was measured. The mean charged-particle multiplicity for inelastic pp collisions was measured to be 7.65±0.17. The prong distribution from 2 to 22 prongs is broader than a Poisson distribution and has a width parameter f2−=〈n−(n−−1)〉−〈n−〉2=0.95±0.21.
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We have extracted the strong interaction form factors from K o e3 and K o μ3 data of our previously reported K o L experiment in a manner which does not assume an explicit q 2 = ( p K − p π ) 2 dependence. We present the unparameterized form factors ƒ + (q 2 ) from the K o L → πeν and K o L → πμν modes and ƒ o (q 2 ) and ξ ( q 2 ) from the K o L → πμν data. A comparison of these unparameterized results is made with the results of the Dalitz plot analyses.
The conventional form factor f+ is studied.
In an exposure of the chamber Mirabelle at the Serpukhov accelerator, 1 943 interactions at 50 GeV/ c and 8 959 at 69 GeV/ c have been observed. Topological cross sections and charged multiplicity distributions are presented. The average charged multiplicities found are respectively 5.32 ± 0.13 and 5.89 ± 0.07.
2PRONG INELASTIC CROSS SECTIONS DERIVED BY SUBTRACTION OF OTHER PRONG CROSS SECTIONS AND KNOWN ELASTIC MEASUREMENTS FROM THE TOTAL.
We present results on vector-meson photoproduction via γp→Vp in the LBL-SLAC 82-in. hydrogen bubble chamber exposed to a linearly polarized photon beam at 2.8, 4.7, and 9.3 GeV. We find ρ0 production to have the characteristics of a diffractive process, i.e., a cross section decreasing slowly with energy and a differential cross section with slope of ∼ 6.5 GeV−2. Within errors the ρ0 production amplitudes are entirely due to natural-parity exchange. s-channel helicity is conserved to a high degree in the γ→ρ0 transition. We find evidence for small helicity-flip amplitudes for ππ pairs in the ρ0 region. Photoproduction of ω mesons is separated into its natural- (σN) and unnatural- (σU) parity-exchange contributions. The Eγ and t dependence and the spin density matrix of the unnatural-parity-exchange contribution are consistent with a one-pion-exchange process. The natural-parity-exchange part has characteristics similar to ρ0 production. At 9.3 GeV the ratio of σ(ρ0) to σN(ω) is ∼ 7. The slope of the φ differential cross section is ∼ 4.5 GeV−2, smaller than that of ρ0 and ω production. Natural-parity exchange is the main contributor to φ production. No evidence for higher-mass vector mesons is found in ππ, πππ, or KK¯ final states. The s and t dependences of Compton scattering as calculated from ρ, ω, and φ photoproduction using vector-meson dominance agree with experiment, but the predicted Compton cross section is too small by a factor of 2.
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THIS HADRON PAIR CROSS SECTION PROVIDES ONLY AN UPPER LIMIT TO THE PION FORM FACTOR ABOVE 1.5 GEV SINCE KAON PRODUCTION IS NOT DISTINGUISHED.
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