Evaluation of the polarization observables I^S and I^C in the reaction gamma p --> pi^0 eta p

TL;DR

This paper presents theoretical predictions for polarization observables I^S and I^C in gamma p --> pi^0 eta p, showing good agreement with recent experimental data and highlighting the role of specific resonances in the reaction.

Contribution

It provides the first theoretical evaluation of I^S and I^C observables using a chiral unitary approach, confirming the dynamical nature of the Delta(1700)D33 resonance.

Findings

Theoretical predictions agree with experimental measurements.

The Delta(1700)D33 resonance plays a key role.

Deviations at high energies suggest additional resonances.

Abstract

We evaluate the polarization observables I^S and I^C for the reaction gamma p --> pi^0 eta p, using a chiral unitary framework developed earlier. The I^S and I^C observables have been recently measured for the first time by the CBELSA/TAPS collaboration. The theoretical predictions of I^S and I^C, given for altogether 18 angle dependent functions, are in good agreement with the measurements. Also, the asymmetry dSigma/dcos(theta) evaluated here agrees with the data. We show the importance of the Delta(1700)D33 resonance and its S-wave decay into eta Delta(1232). The result can be considered as a further confirmation of the dynamical nature of this resonance. At the highest energies, deviations of the predictions from the data start to become noticeable, which leaves room for additional processes and resonances such as a Delta(1940)D33. We also point out how to further improve the calculation.