Data on polarization in backward elastic π + p scattering at 2.0, 3.5 and 4.0 GeV/ c are presented. The data at 2.0 GeV/ c are compared with the result of a recent phase-shift analysis. Our data at 3.5 and 4.0 GeV/ c , and existing data above 3 GeV/ c , show no significant energy dependence of the polarization over the measured u -range. A comparison with Regge models and with results from amplitude analysis is made.
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The differential cross section has been measured for the reaction γ +p→p+ π o at the Bonn 2.5 GeV electron synchrotron in the energy range from 0.4 to 2.2 GeV for a c.m. angle of 150 degrees. The protons were detected in a magnetic spectrometer system. The excitation curve shows a distinct resonance structure. The total corrections to the counting rate are about 3%. The contribution of the process γ +p→p+2 π was separated. The uncertainty of this separation leads to an error of about 4% in the cross section.
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Topological and channel cross sections are given for the more common final states produced in K − p interactions at 8.25 GeV/ c together with the single particle inclusive cross sections. We present cross sections for prominent resonances occurring in final states K N (nπ) and find the resonance fractions to be roughly independent of multiplicity.
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We present results of measurements of K ± p and p p elastic scattering and of the annihilation reactions p p →π + π − and p p → K + K − at an incident laboratory momentum of 5 GeV/ c . Nearly complete angular distributions were obtained. Results are also presented for π -meson proton elastic scattering in the momentum transfer ranges 2 < − t < 8 (GeV/ c ) 2 (for π + ) and 0.16 < − t < 7 (GeV/ c ) 2 (for π − ). All measurements were done in one experimental geometry. The measured differential cross sections range from 10 to 10 −5 mb/(GeV/ c ) 2 .
-U = T + 8.486 GEV**2.
THE DATA FOR -T = 7.31 TO 8.45 GEV**2 WERE NORMALIZED TO OTHER EXPERIMENTS.
-U = T + 8.304 GEV**2.
Inclusive photoproduction cross sections for pions, kaons and protons have been measured in the photon fragmentation region and are compared with recent electroproduction data at q 2 = 1.16 (GeV/ c ) 2 . If the cross sections are normalized to the total hadronic cross sections at q 2 = 0 and q 2 = 1.16 (GeV/ c ) 2 , respectively, we observe that more pions, about an equal number of protons, but fewer kaons are found in the photoproduction case for x ≥ 0.3.
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We have measured the mean charged multiplicity n¯CH as a function of transverse momentum p⊥ of the forward proton in the reaction p+p→p+MM for five intervals of missing mass (MM) using our Multiparticle Argo Spectrometer System. We observe an increase of n¯CH for p⊥>1 GeV/c.
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Measurements of the polarization parameter of the reactions π − p → π 0 n and π − p → η n at 4.90 and 7.85 GeV/ c and for a squared four-momentum transfer − t ranging from 0.1 to 2.0 (GeV/ c ) 2 have been achieved by using a butanol polarized proton target and detecting only the two γ's from the neutral meson decay. The background due to events involving bound protons has been separately measured and subtracted out. A large positive polarization has been found for the reaction π − p → π 0 n. It is consistent with other pion-nucleon scattering data connected by isospin conservation. The polarization for the reaction π − p → η n is not significantly different from zero within the large experimental errors.
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The total cross sections of 4 He, 6 Li, 7 Li, 9 Be, 12 C and 32 S for positive and negative pions have been measured in the energy range 80 to 260 MeV in a transmission experiment. Coulomb corrections were applied using real parts of the forward nuclear amplitudes as determined from dispersion relations. At the lower energies there remain large residual differences between the π + and π − scattering on the isoscalar nuclei. These can be largely understood in terms of the Coulomb distortion.
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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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