Spin Transfer In Pp Elastic Scattering At 198 Mev: Implications For The Pi Nn 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 Facility. The new data span a kinematic regime chosen specifically to maximize sensitivity to the neutral pi NN coupling constant. Our results provide strong support for modem potential models of the NM interaction in which a relatively weak pion coupling (g(0)(2) approximate to 13.6, f(0)(2) approximate to 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-exchange framework indicate that most of these latter differences can be removed by reducing g(0)(2) from 14.4 to 13.6 in these models.