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Polarized proton induced exclusive pion production on ¹⁰B and ⁹Be for incident energies from 200 to 260 MeV Ziegler, William Anthony


Two sets of experiments for studying polarized proton induced exclusive pion production were performed at TRIUMF. The angular distributions of both the differential cross-sections and analyzing powers are presented for: ¹⁰B(ρ[sup →], π⁺)¹¹B[sub g.s.,2.12[sub MeV], ⁹BE(ρ[sup →], π⁺)¹⁰BE[sub g.s.,3.37[sub MeV], and ⁹BE(ρ[sup →], π⁻)¹⁰C[sub g.s.,3.34[sub MeV] for incident proton energies between 200 and 260 MeV. The results indicate a number of new trends in pion production. The preference for populating high-spin final states (at least in these reactions) seems to be primarily a spin statistical weighting effect. The dependence of the shape of the angular distributions on incident proton energy is linked with the quantum numbers of the final state nucleus. Transitions to a final state that can be described as single-particle have a strong and similar energy dependence. In contrast transitions to the other states, those that cannot be described as having a single-particle nature show a weak energy dependence. The diffractive forward angle peaking which is common to most pion production differential cross-section distributions was found to have exponential slopes consistent with production radii of the single nucleon size rather than that of the nucleus. Finally, the results are compared to predictions of current theoretical models of pion production. Failures of these models are discussed and suggestions for improvements offered.

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