The polarization of the proton produced by the photodisintegration of the deuteron has been measured at several angles for photon energies between 170 and 450 MeV. The polarization is found to be around -0.20 (Basel convention) for 90° c.m. and photon energies between 200 and 300 MeV. This is in reasonable agreement with a calculation by D. George based upon the Austern model. However, the calculation fails to explain the strong increase in polarization with increasing photon energies. At a photon energy of 450 MeV and 90° c.m. the proton polarization is as large as -0.60.
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Cross sections for π0 photoproduction from hydrogen in the backward direction have been measured for photon energies of 6, 8, 12, and 18 GeV. The range of momentum transfer covered in these measurements is −1 (GeVc)2
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Measurements on large-angle photoproduction of π+ mesons from hydrogen have been made at the Stanford Linear Accelerator Center for photon energies between 5 and 15.5 GeV and u values from +0.05 to -1.8 (GeV/c)2. The measured cross section decreased with energy approximately as k−3, showing no shrinkage in this range of u values. Furthermore, it had a smooth u dependence with no sign of a dip at u≃−0.15 (GeV/c)2 as would be expected from nucleon exchange. π−Δ++ production was measured at 5 GeV and shows a rapid decrease with increasing |u|.
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Measurements have been made on Compton scattering for photon energies between 5 and 17 GeV and t values from -0.06 to -1.1 (GeVc)2. The data were obtained by performing a coincidence between the Stanford Linear Accelerator Center 1.6-GeVc spectrometer and a Lucite shower counter. The scattering appears diffractive out to high t values, but the cross sections seem not to be in good agreement with the prediction of a strict vector-meson-dominance model.
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We present cross sections and angular distributions for the reaction K + d → K o pp at 865, 970, 1210, 1365 and 1585 MeV/ c . Making corrections for deuterium effects, we observe the following features of the elastic charge exchange process K + n → K 0 p: a) the c.m. angular distribution becomes increasingly peripheral as the momentum increases from 800 to 1600 MeV/ c ; b) the forward amplitude is largely real. Attempts to describe the data either in terms of a Regge model or in terms of dominance by an elastic P 1 2 isoscalar KN resonance are discussed.
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A study of the A2+ mass spectrum in π+p interactions at 3.7 GeVc is presented. For a cut of t′=0.1−2.0 GeV2 and on eliminating the Δ++ we find that the three-pion mass spectrum in the A2+ region is fitted by the dipole formula with a confidence level of 53% and a single Breit-Wigner formula with a confidence level of 11%. Our result thus favors A2+ splitting although a single Breit-Wigner fit cannot be ruled out. We also report the A2+ decay branching fractions measured over all t′ values. They are 0.78 ± 0.05, 0.15 ± 0.04, 0.06 ± 0.03, and < 0.02 for ρπ, ηπ, KK¯, and η′π, respectively, in good agreement with other experiments.
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We have completed measurements of the differential cross section for γ+p→π0+p, and the asymmetry with polarized photons, for incident photon energies from 4 to 18 GeV and momentum transfers between t=−0.1 and −1.4 (GeV/c)2. The experiment was performed at the Stanford Linear Accelerator Center, using the SLAC 1.6-GeV/c spectrometer to analyze protons recoiling from a hydrogen target. For the cross-section measurements a normal collimated bremsstrahlung beam was used. For the asymmetry measurements the polarized photons were produced by coherent bremsstrahlung from a diamond crystal, and a coincidence was required between the recoil proton and one of the π0 decay photons in a shower counter.
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The Λ polarization in the reaction γp → K + Λ has been measured using the decay Λ → pπ − as an analyzer. It is found to be large and negative in the momentum transer range 0.2 ⩽ | t | ⩽ 1.0 (GeV/ c ) 2 .
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We have measured the asymmetry parameter Σ=(σ∥−σ⊥)(σ∥+σ⊥) for the photoproduction of ϕ mesons with photons polarized parallel and perpendicular to the plane of decay for the reaction γp→ϕp→K+K−p. We find Σ=0.985±0.12 at a photon energy of 8.14 GeV and |t| of 0.2 (GeVc)2, consistent with pure diffraction production, or pure naturalparity Regge exchange.
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The joint decay density-matrix elements have been measured for the ρ0Δ++ and ωΔ++ channels at 3.7 GeV/c. The data are presented as a function of momentum transfer in both the t-channel and s-channel coordinate systems. The presence of correlated decays is illustrated for both reactions by employing selective cuts on the decay angles of one resonance, and displaying the effects on the decay distribution of the opposing resonance. An amplitude analysis is performed with the data near 0° production angle, where we obtain a helicity decomposition of the scattering amplitude with no experimental ambiguity.
T-CHANNEL COORDINATE SYSTEM (XYZ=TH).
T-CHANNEL COORDINATE SYSTEM (XYZ=TH).
S-CHANNEL COORDINATE SYSTEM (XYZ=SH).
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