NN Scattering and Nucleon Quark Core

We review here nucleon-nucleon elastic and charge exchange scattering with special emphasis on the quark hard core inside the nucleon. It is found that total cross sections are sensitive only to the total hadronic size of the proton, which has two components, the quark core and the surrounding meson cloud. At higher energies differential cross sections are found to reveal, for larger -t, a hard core size of order ~ 0.3 fm. We present model calculations for unpolarized cross sections and find that a meson exchange model with QCD vertex functions reflecting the quark/antiquark structure of the nucleon is well capable of reproducing existing data. A quark core size of order 0.3 fm is found in our model and a preference for certain meson exchanges. As expected the pion exchange supplemented with,, ƒ0, ƒ2, a2 dominates the t-dependence of the elastic cross sections while isovector exchanges π,, a2 with a background field dominate the charge exchange n-p reaction.