2022/07/28 by S. Garni, Garni, S., V. L. Kashevarov +164
Engineering · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Nuclear physics research studies #Quantum Chromodynamics and Particle Interactions #Superconducting Materials and Applications
paper · pdf · doi:10.48550/arxiv.2207.14079
openalex publication_date 2022/07/28 · openalex created_date 2022/07/30 · openalex updated_date 2026/07/28
Background: Photoproduction of pion pairs allows to study sequential decays of nucleon resonances via excited intermediate states. Such decays are important e.g. for states which in the quark model have both oscillators excited and de-excite them in a two-step process. However, analyses of multi-meson final states is difficult and requires more than unpolarized cross section measurements. Purpose: Experimental study and model analysis in view of resonant contributions of target and beam-target polarization observables for the reaction γp → π0 π0 p. Methods: Investigated were target (single) and beam-target (double) polarization asymmetries in dependence of several parameters. The experiments were performed at the Mainz Microtron (MAMI) using circularly polarized photon beams and transversally polarized solid-state butanol targets. The reaction products were analyzed with the Crystal Ball and TAPS detectors. Results: Studied were the polarization observables Py (unpolarized beam, target polarized in y direction) and Px (circularly polarized beam, target polarized in x direction), which are similar to T (target asymmetry) and F (beam-target asymmetry) for single pion production. The asymmetries were analyzed with three independent methods, revealing systematic uncertainties.