Measurement of the beam-helicity asymmetry in photoproduction of $\ddot{I}{€}^0\hat{I}\cdot$ pairs on carbon, aluminum, and lead

Abstract

The beam-helicity asymmetry was measured, for the first time, in photoproduction of $\ddot{I}{€}^0\hat{I}\cdot$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for $\ddot{I}{€}^0\hat{I}\cdot$ pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the $D_{33}$ partial wave with the $\hat{I}\cdot \hat{I}”(1232)$ intermediate state.

Accepted for publication in Physics Letters B (2020)