How Sensitive are Various NN Observables to Changes in the pNN Coupling Constant?

The deuteron, NN analyzing powers A_y, and the singlet scattering length show great sensitivity to the $pi NN$ coupling constant $g_pi$. While the pp A_y data favor $g^2_pi/4pileq 13.6$, the np A_y data and the deuteron quadrupole moment imply $g^2_pi/4pigeq 14.0$. The two diverging values could be reconciled by the assumption of (substantial) charge-splitting of $g_pi$. However, the established theoretical explanation of the charge-dependence of the $^1S_0$ scattering length (based upon pion mass splitting) is very sensitive to a difference between $g_{pi^0}$ and $g_{pi^pm}$ and rules out any substantial charge-splitting of $g_pi$. Thus, there are real and large discrepancies between the values for $g_pi$ extracted from different NN observables. Future work that could resolve the problems is suggested.Comment: Latex, 19 pages, 4 figures; invited talk presented at the Workshop on `Critical Points in the Determination of the Pion-Nucleon Coupling Constant', Uppsala (Sweden), June 7-8, 199