0000000000515739

AUTHOR

Byron K. Jennings

Asymmetries in elastic scattering of 100 MeVπ+from a polarizedHe3target

We report the observation of a large asymmetry in the elastic scattering of 100 MeV {pi}{sup +} from a polarized {sup 3}He target. Measurements have been made at laboratory angles of 60{degree}, 80{degree}, and 100{degree}, with the largest value {ital A}{sub {ital y}}=0.89{plus minus}0.12 occurring at 80{degree}, near a cross-section minimum. This asymmetry is the largest observed to date in pion scattering from a spin-1/2 nucleus. The {ital A}{sub {ital y}} data are qualitatively reproduced by a schematic model; however, agreement with the data is significantly improved when realistic three-body Faddeev wave functions and a full nonlocal distorted-wave impulse approximation reaction model…

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Pion Scattering and Pion Photoproduction on 3He

Using realistic 3-body Faddeev wave functions π± scattering and π+ photoproduction on 3He have been calculated in a consistent model. We demonstrate that at T π ≤ 180MeV polarization observables in pion scattering contain very little information about nuclear structure and can be understood in terms of free πN amplitudes. At higher energies the sign-flip of the asymmetry A y offers a new possibility to study higher-order effects of pion nuclear interaction. In pion photoproduction we find that two-step processes such as 3 He(γ, π°)3 He(π°, π+)3 H give rise to unexpected large contributions to the differential crosssection as well as to γ-asymmetry and with this improved a long time discrepa…

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The asymmetry in π−3He scattering

Abstract We show that the π + − 3 He asymmetry data obtained in a recent TRIUMF experiment at T π = 100 MeV can be understood in terms of the elementary π N amplitudes. Through a comparison to a full optical-potential calculation that employs realistic Faddeev wave functions for the trinucleon we show that all nuclear-structure dependence cancels for A y at lower energies. At higher pion energies around the Δ-resonance region the sign flip of A y offers the possibility of extracting information about the smaller partial waves.

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