Determination of the analysing power for the $\vec{p}p \rightarrow   pp\eta$ reaction using WASA-at-COSY detector system
  We report on the measurement of the analyzing power for the (vec)pp->ppeta reaction with beam momenta of 2026 MeV/c and 2188 MeV/c performed with the WASA-at-COSY detector at the Cooler Synchrotron COSY. The eta meson from the (vec)pp-> ppeta reaction was identified by the techniques of missing mass and invariant mass. The angular distribution of the determined analyzing power strongly disagree with theoretical predictions. A comparison of the obtained Ay angular distribution with a series of associated Legendre polynomials revealed negligible contribution of the Sd partial wave at Q = 15 MeV. However, at Q = 72 MeV, a significant interference of the Ps and Pp partial waves was observed. 
I. Schaetti-Ozerianska, P. Moskal, M. Zielinski
nucl-ex hep-ex