Determination of the analysing power for the $\vec{p}p \rightarrow pp\eta$ reaction using WASA-at-COSY detector system

TL;DR

This study measures the analyzing power in proton-proton to proton-proton eta reactions at specific energies, revealing discrepancies with theoretical models and insights into partial wave contributions.

Contribution

First measurement of the analyzing power for the pp->ppeta reaction at these energies using the WASA-at-COSY detector, providing new experimental data.

Findings

Disagreement between measured analyzing power and theoretical predictions.

Negligible Sd partial wave contribution at Q=15 MeV.

Significant Ps and Pp partial wave interference at Q=72 MeV.

Abstract

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.