For the reaction γ+p→γ′+p′ (proton Compton effect), we have measured the ratio dσIIdσ⊥ between the cross sections for linearly polarized photons, using the coherent bremsstrahlung beam of the Frascati electron synchrotron. At 90° in the c.m. system and in the photon energy region 300≤K≤335 MeV, we find dσIIdσ⊥=2.1−0.4+0.5. In the absence of theoretical predictions based on the dispersive theory in this energy region, this result is compared with the values obtained using an isobaric model, taking into account various possible intermediate states.
Axis error includes +- 0.0/0.0 contribution (?////).
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The angular distributions of K<sup loc="post">+</sup>p and π<sup loc="post">+</sup>p backward elastic scattering have been measured at 5.2 and 6.9 GeV/c. Backward π<sup loc="post">-</sup>p and K<sup loc="post">-</sup>p elastic scattering were studied at 6.9 GeV/c. Backward peaks are observed in K<sup loc="post">+</sup>p scattering with an energy dependence of the form s<sup loc="post">−4</sup>.
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The reactions π−p→π−p and π−p→π−π0p for 1.7 GeV/c incident π− have been studied, in 3094 and 2244 interactions respectively, identified from 10 106 two-prong events measured in film exposed at the BNL 20 in. hydrogen bubble chamber. The differential elastic-scattering cross-section is found to show a first and second diffraction peak and a first diffraction minimum with indications of a second minimum and onset of a third maximum. The experimental curve has been fitted by a black-dise optical-model formula with radius (0.80±0.03) fm and by a differential cross-section computed from the Dirac equation depending on two ranges, 0.7 fm attractive imaginary and 0.4 fm repulsive. The dominant mode (∼40%) of the π−π0p production is through the two-body channel, π−p→ϱ−p. We find the following cross-sections: σ(π−p→π−p mb, σ(π−p→π−p mb. The differential rhomeson production cross-section shows a diffraction peak having a dependence (dσ/dt)(π−p→ϱ−p)=[(2.5±0.2) exp [(−5.3±0.5)t]] mb/(GeV/c)2, wheret is the squared four0momentum transfer between incoming and outgoing proton in (GeV/c)2, and a second diffraction maximum. It has been fitted by an optical-model formula for a bright ring of radius 0.80 fm and ring thickness 0.25 fm. The cross-section for σ(π−p→π−p was found to be (0.36±0.04) mb. From the inelastic data the Chew-Low dipion scattering cross-section has been computed, using various form factors. A form factor of unity is found to be acceptable.
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