Determination of the analysing power for the $\bar{p}p$ →ppηreaction using the WASA-at-COSY detector system

Abstract

Abstract. High statistics measurements of the analyzing power for the pp → ppη reaction were performed with the WASA-at-COSY detector at the Cooler Synchrotron COSY. The η meson was produced at two excess energies: Q = 15 MeV and Q = 72 MeV, and it was registered using the missing and invariant mass techniques. The determined analyzing power is consistent with zero for Q = 15 MeV implying the dominance of s wave and an insignificant contribution of the S d partial wave. However, at Q = 72 MeV the angular distribution of the analyzing power reveals a strong interference of Ps and Pp partial waves. Moreover, the available theoretical predictions for the angular dependence of the analyzing power strongly deviate from our experimental results.

Production and interaction of theηmeson with nucleons and nuclei

“…The data was gathered for two separated beam momenta 2026 MeV/c and 2188 MeV/c, which correspond to excess energy over the η production threshold of 15 MeV and 72 MeV, respectively. More details of the analysis can be found in [26].…”