A measurement of the spin transfer observable D_NN′ for p+p elastic scattering at T_p=200 MeV

Recent analyses of NN and πN scattering data have resulted in values for the πNN coupling constant which are significantly smaller than those obtained prior to 1987. These controversial results prompted us to investigate the usefulness of high‐quality spin measurements towards resolving this issue. We found that the normal component spin transfer observable D_NN′ for p+p elastic scattering is very sensitive to g²₀, particularly at small angles. We have therefore determined precise values of D_NN′ for this reaction for θ_lab=5.0°, 7.2°, 8.4°, 9.7°, 11.8°, 14.6°, 18.8°, 24°, 30°, and 38° at an incident beam energy of 200 MeV. The forward‐going proton was detected in the IUCF K600 spectrometer and the coincident recoil proton was detected in a Si/CsI detector telescope. Our preliminary D_NN′ values are reproduced reasonably well by Arndt’s C200 solution, the Nijmegen PWA93, and the Nijmegen I potential, but differ severely from both Arndt’s SM94 global solution and the predictions of the Bonn potential.