In-medium NN interactions and nucleon and meson masses studied with nucleon knockout reactions

Spin observables have been measured for (p, 2p) reactions aiming at studyin g medium effects on NN interactions in nuclear field. Observed strong densi ty-dependent reduction of the analyzing power is consistent with a model ca lculation where reduction of nucleon and meson masses are taken into accoun t. On the other hand, calculations with g-matrices in the Shrodinger framew ork does not predict the reduction. The spin-transfer coefficients, which d ata are not reproduced by the model calculation, are found to be sensitive to reduction rate of each meson mass and have a possibility to test scaling lows in mass reductions.