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A theoretical study of the (π,πn) knock-out reaction Shrimpton, Neil Douglas


The (π, πn) reaction is studied theoretically, the specific case examined being 0¹⁶(π⁺, π⁺p)N¹⁵. Calculations of the differential cross sections for 1P ½ and 1P 3/2 protons are made at various incident pion energies. The remaining kinematic variables are specified by a geometry which emphasizes the behavior of the two-body pion nucleon interaction. The aim is to examine the influence of the nucleus on the two-body interaction. In particular, the influences of Pauli exclusion of the nucleon, the off-shell effect, and the effective polarization of the nucleon are examined. The computation is performed using the factorized distorted wave impulse approximation. By evaluating the distorted wave matrix element in coordinate space the localization of the knock-out reaction in the nucleus is determined. The Pauli exclusion of the nucleon is found to have the largest influence on the differential cross section at incident pion energies of 116 MeV. At higher energies the knock-out reaction occurs at the extreme edge of the nucleus and the effect of Pauli exclusion is minimal. At lower energies, the two-body interaction itself is less sensitive to Pauli exclusion. Off-shell effects were found to be very small. The polarization of the proton was found to have a large influence on the cross sections. Furthermore, it is noted that comparing the cross sections for 1P ½ and 1P3/2 protons will indicate the effective polarization of the proton in the nucleus.

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