Baryon spectroscopy - Recent results from the CBELSA/TAPS experiment

Abstract

Abstract. One of the remaining challenges within the standard model is to gain a good understanding of QCD in the nonperturbative regime. One key step toward this aim is baryon spectroscopy, investigating the spectrum and the properties of baryon resonances. To get access to resonances with small πN partial width, photoproduction experiments provide essential information. In order to extract the contributing resonances, partial wave analyses need to be performed. Here, a complete experiment is required to unambiguously determine the contributing amplitudes. This involves the measurement of carefully chosen single and double polarization observables. The CBELSA/TAPS experiment with a longitudinally or transversely polarized target and an energy tagged, linearly or circularly polarized photon beam allows the measurement of a large set of polarization observables. Due to its good energy resolution, high detection efficiency for photons, and the nearly complete solid angle coverage, it is ideally suited for the measurement of photoproduction of neutral mesons decaying into photons. Recent results for various double polarization observables in π 0 and η photoproduction and their impact on the partial wave analysis are discussed.