Eta photoproduction in a combined analysis of pion- and photon-induced reactions

Abstract

The ηN final state is isospin-selective and thus provides access to the spectrum of excited nucleons without being affected by excited ∆ states. To this end, the world database on eta photoproduction off the proton up to a center-of-mass energy of E ∼ 2.3 GeV is analyzed, including data on differential cross sections, and single and double polarization observables. The resonance spectrum and its properties are determined in a combined analysis of eta and pion photoproduction off the proton together with the reactions πN → πN , ηN , KΛ and KΣ. For the analysis, the so-called Jülich coupled-channel framework is used, incorporating unitarity, analyticity, and effective three-body channels. Parameters tied to photoproduction and hadronic interactions are varied simultaneously. The influence of recent MAMI T and F asymmetry data on the eta photoproduction amplitude is discussed in detail.

Study of QCD-dynamics inηandη′production and decays

“…6(a) and 6(b)). Furthermore the different partial wave analyses (solutionsBnGa2014-01, BnGa2014-02 [35], the SAID-GE09 [34] and the JüBo2015 fit B [32]) agree well with the data since the existing data have been included in all solutions. Above 1500 MeV no data exist until now.…”

Modern Dynamical Coupled-Channels Calculations for Extracting and Understanding the Nucleon Spectrum

“…Here, our results from Refs. [7,8] are compared with those obtained from the other coupled-channels analyses by the Jülich [19] and Bonn-Gatchina [20] groups. One can see that the existence and mass values agree very well for the lowest states in most spin-party states.…”

“…In the analysis, we use the so-called structure functions as the data to analyze, which were installed in our analysis with the help of K. Joo and L. C. Smith [26]. We see that our current results [8] and dashed [7] lines are the results from the ANL-Osaka analyses, while the blue and green solid lines are the results from the Jülich (Model B of [19]) and Bonn-Gatchina [20] analyses. The spectra of fourand three-star resonances rated by PDG [2] are also presented with the red and blue filled squares, respectively, which represent the range of the resonance masses assigned by PDG.…”

Nuclear reactions at intermediate energies

“…The effective methods that are used to describe the dynamics of meson production reactions, include explicitly the baryon resonance states whose properties are extracted by comparing the predictions of the theory with the experimental data [9][10][11][13][14][15][16][17]. However, for a reliable realization of this goal, a model is required that can analyze different reactions over the entire energy range using a single Lagrangian density, which generates all non-resonance contributions from Born, u-and t-channel contributions without introducing new parameters.…”