Final states π − Σ + , π + Σ − , π o Λ and ηΛ were studied for K − p reactions at 3.95 GeV/ c . Cross sections, angular distributions and polarizations are presented. Data for π − Σ + and π o Λ production are compared to the line-reversed πp reactions at the same beam momentum. Baryon-exchange peaks are presented for the Σ + π − , Σ − π + and Λπ o final states.
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It is found in the reactions π ± p →( π ± π + π − )p, believed to be dominated by diffraction dissociation, that the d σ d t′ distributions show a “cross-over” effect at t ′ ≈ 0.15, similar to the effect observed in elastic scattering. This gives evidence for the interference of ( ϱ 0 , B 0 ,…)-exchanges with ( P , f 0 , …) -exchanges in pion diffraction dissociation reactions. No such evidence is found for baryon dissociation, π ± p → π ± (p π + π − ), at the same energy.
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Multihadronic production has been observed at the Adone e + e − storage ring, in the c.m. energy range 1.4 - 2.4 GeV. The cross sections for the reactions e + + e − → 2 π ± + nπ o (1 ⩽ n ⩽ 4) and e + + e − → (4 π ± + nπ ± ) (0 ⩽ n ⩽ 2) have been measured, assuming that the produced particles are only pions with a pure phase space momentum distribution.
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Differential cross sections for single photoproduction of neutral pion on neutron have been measured at different c.m. angles for photon energies, between 450–800 MeV.
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The elastic scattering of K ± mesons on protons has been studied at 5 GeV/c. A total of about 500 000 events have been measured in the c.m. angular range 17° < θ cm < 165° corresponding to 0.2 < − t < (GeV/ c ) 2 . We observed a K − p backward peak which we have parametrized as d σ /d u = (0.6 ± 0.2) exp [(3.3 ± 0.6) u ] μb /(GeV/c) 2 , while for the K + p backward peak we find d σ /d u = (17.5 ± 1) exp [(3.6 ± 0.2) u ] μb /(GeV/c) 2 . The K − p cross-section falls to about 0.03 μ b ( GeV /c) 2 around − t = 5 (GeV/ c ) 2 , while the K + p cross-section stays in the vicinity of 0.3 μ b ( GeV /c) 2 in the same t -region. The K + p and K − p differential cross-sections have cross-over points at − t = 0.2, 1.1 and about 3.5 (GeV/ c ) 2 .
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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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Polarization distributions and differential cross section data for elastic scattering of negative pions on protons between 865 and 2732 MeV/ c are presented. They are compared with published phase-shift analyses.
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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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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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