Measurement of spin asymmetry parameters in the [reaction proton + proton --> proton + neutron + positive pion using a polarized hydrogen target and a polarized proton beam]

Measurements have been made of the spin asymmetry parameters A[sub NN], A[sub LL], A[sub SS], A[sub SL], A[sub NO] and A[sub ON] in the inelastic reaction pp → pn π⁺ at incident beam energies of 510, 465 and 420 MeV. The measurement of A[sub NN] is described specifically. This experiment has reported the first results of a spin asymmetry measurement with a polarized beam and polarized target in a reaction having a three particle final state. Neutrons were detected in an array of position sensitive scintillation counters while the two charged particles were detected in an array of multi-wire proportional chambers. Time of flight was recorded for the neutron. Events were kinematically reconstructed in the analysis program in which free and quasi-free scattering events were separated by a X² test to the kinematical fit. The unpolarized background from non-hydrogenous material in the target was estimated from unpolarized data obtained with the target material replaced by teflon. Results are presented as asymmetries binned against single kinematic variables. The statistical precision is 10% on the best data. The data are sufficiently complete to identify the dominant partial wave amplitudes. A comparison is made with calculations based on a one-pion-exchange Δ dominance model. Discrepancies from the model are attributed the neglect of the TTN S₃₁ interaction in the calculations.