Testing microscopic medium effects on nucleons and mesons using polarization observables in high-spin, unnatural-parity ((p)over-right-arrow, (p)over-right-arrow ') reactions at 200 MeV - art. no. 014309

We compare measurements of the cross section, analyzing power, induced pola rization, and polarization transfer coefficients for ((p) over bar,(p) over bar') reactions leading to unnatural-parity, high-spin states in O-16 and Si-28 with distorted wave impulse approximation calculations. We use an eff ective nucleon-nucleon (NN) interaction obtained from a microscopic treatme nt of nuclear medium effects. The NN potential is generated from a one-boso n-exchange model of the nuclear force that reproduces NN scattering data we ll. Medium effects are incorporated through a G matrix obtained within a Di rac-Brueckner approach to nuclear matter. While agree ment for some observa bles is good, differences for the polarization transfer coefficients indica te that systematic problems with the relative sizes of the spin-orbit and t ensor interaction components exist. The differences are larger for Si-28 th an for O-16. A new model that incorporates density-dependent meson mass red uctions produces only small effects that do not change the quality of the a greement. Connections to previous calculations are investigated.