Study of the production mechanism of the eta meson by means of analysing   power measurements
  Information about the production mechanism of the eta meson in proton-proton collisions can be inferred by confronting the experimental studies on the analysing power for the p(pol)p --> pp eta reaction with the theoretical predictions of this observable. Results show that the predictions of pure pseudoscalar- or vector meson exchange model are insufficient to describe the analysing powers. 
R. Czyzykiewicz, P. Moskal, H.-H. Adam, A. Budzanowski, E. Czerwinski,   D. Gil, D. Grzonka, M. Janusz, L. Jarczyk, B. Kamys...