The angular dependence of the asymmetry for negative-pion photoproduction on neutrons by linearly polarized photons has been measured for photon energies 260, 300, 350, 400, 450, and 500 MeV at center-of-mass angles 60°, 75°, 90°, 150°, and 120°. The results are compared with theoretical models of low-energy single-pion photoproduction. The observed asymmetry below 400 MeV shows good agreement with predictions of dispersion-theoretical models by Berends, Donnachie, and Weaver and by Schwela. The asymmetry values in the 400-500 MeV energy region suggest that smaller M1− amplitude is more favorable.
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The reactions\(\bar pp \to \bar \Lambda \Lambda \),\(\bar \Lambda \Sigma ^0+ C.C.\),\(\bar \Sigma ^ +\Sigma ^ +\) and\(\bar \Sigma ^ -\Sigma ^ -\) are studied at 2.2 GeV/c. The cross-section, differential cross-section, polarization and spin correlations (between the\(\bar \Lambda \) and Λ hyperons) are discussed.
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LAMBDA AND ALAMBDA POLARIZATIONS ASSUMED EQUAL. SPIN CORRELATIONS ALSO ESTIMATED.
The K − p reactions with final states Λπ 0 , Σ 0 π 0 , Λπ 0 π 0 , Λη and Σ 0 η have been studied at 14 momenta between 685 and 934 MeV/ c using optical spark chambers. The charged decay products of the Λ are detected by low mass spark chambers while γ-rays from π 0 and Σ 0 decays are detected in high mass chambers. Approximately 250 000 photographs were analysed from which partial and differential cross sections were determined. These results are presented with an energy dependent, single channel partial-wave analysis.
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The π − p→n γ and π − p→n π ° differential cross sections have been measured for −0.9< cos θ ∗ <−0.45 (θ ∗ c.m. scattering angle) at 475 MeV/ c and 550 MeV/ c incident momenta. The π − p→n γ measurement is a good check of the detailed balance principle in the electromagnetic interactions of hadrons at these energies and is in good agreement with Walker's analysis. On the other hand the π − p→ π °n extrapolated values of 180° allows one to verify that the phases of the A 1 2 and A 3 2 amplitudes are equal.
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BACKWARD CROSS SECTION ESTIMATED BY LEGENDRE POLYNOMIAL FIT.
A systematic analysis is presented on the reaction K + p → K ∗0 (890) Δ ++ for nine incident momenta between 4.6–16.0 GeV/ c . Cross sections, differential cross sections and vector meson single density matrix elements are given. As a function of energy, little if any change is observed in either the shapes of the differential cross sections or in the values of the density matrix elements. The data are interpreted in terms of current ideas on t -channel exchange mechanisms.
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The results of the total cross section measurements of neutrons on protons, deuterons and nuclei C, O, Al, Cu, Sn, Pb in the energy range of 28–54 GeV are reported.
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We have measured the total inelastic cross section (σinel) and charged-particle multiplicities obtained in pp collisions at 405 GeV/c. The data are from a preliminary 12 000-picture bubble-chamber exposure. We find σinel=32.8±1.0 mb; the low moments of the multiplicity distribution for negative particles are 〈n−〉=3.50±0.07, D−=2.37±0.05, f2−=2.1±0.2, and f3−=0.1±0.9. We also present updated results at 102 GeV/c.
SUPERCEDES PRELIMINARY RESULTS IN J. W. CHAPMAN ET AL., PRL 29, 1686 (1972).
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FIT TO ELASTIC DIFFERENTIAL CROSS SECTION FOR 0.05 < -T < 0.7 GEV**2.
Measurements are presented of the recoil-proton polarization for π0 photoproduction angles near 64° in the c.m. system. The steep angular dependence observed by others at lower energies persists to at least 1500 MeV, and the polarization crosses through zero near 63° over the entire 900-1600-MeV energy interval. Summary fits are made to available recoil-proton polarization data, 950-1250 MeV, and are found to require terms of order cos3θ, but no higher.
Axis error includes +- 0.0/0.0 contribution (?////).
We have measured the ratio of the cross section for γ+n→π0+n to the cross section for γ+p→π0+p at 4.7 and 8.2 GeV. The measurements were made by detecting the recoil nucleons in coincidence with the decay γ rays of the π0's produced from a deuterium target. At 4.7 GeV the cross-section ratio, R≡σ(γ+n→π0+n)σ(γ+p→π0+p), is less than 1.0 at low t, with an indication of a dip at about t=−0.7(GeVc)2, and rises to 1.0 at high t. The ratios at the higher energy have less structure and are uniformly closer to 1.0.
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