Spin Transfer inppElastic Scattering at 198 MeV: Implications for theπNNCoupling Constant

A precision measurement of spin transfer in $\mathrm{pp}$ 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 $\pi \mathrm{NN}$ coupling constant. Our results provide strong support for modern potential models of the $\mathrm{NN}$ interaction in which a relatively weak pion coupling ( $g_0^2\approx 13.6$, $f_0^2\approx 0.075$) is employed, but disagree significantly with predictions of older models in which $g_0^2\approx 14.4$. 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.