Spin transfer in pp elastic scattering at 198 MeV: Implications for the piNN coupling constant

A precision measurement of spin transfer in pp elastic scattering at 197.8 MeV has been completed recently at the Indiana University Cyclotron Facilit y. The new data span a kinematic regime chosen specifically to maximize sen sitivity to the neutral pi NN coupling constant. Our results provide strong support for modem potential models of the NM interaction in which a relati vely weak pion coupling (g(0)(2) approximate to 13.6, f(0)(2) approximate t o 0.075) is employed, hut disagree significantly with predictions of older models in which g(0)(2) approximate to 14.4. Calculations in a one-boson-ex change framework indicate that most of these latter differences can be remo ved by reducing g(0)(2) from 14.4 to 13.6 in these models.