The pion-nucleon coupling constant and its sensitivity to the backward angle n-p differential cross section

Recent accurate measurements of the n-p differential cross section in the backward angle region at 96 MeV laboratory energy are about 10% higher than previous experiments. Preliminary data at higher, energies indicate the same tendency. Modern potential models for the NN interaction under predict these new data and this has been Misinterpreted as an indication for a stronger tensor force than generally assumed. We have investigated in detail the sensitivity of the differential cross section at backward angles to isospin singlet phase shift parameters for various energies in the framework of meson exchange models. A sensitivity to high partial waves, dominated by the one-pion exchange, as well as to D-wave contributions was found. We study the influence of the pion as well as rho coupling in the backward angle regime between 65 and 200 MeV