Coupled-channel contributions to the GDH sum rule from the Jülich–Bonn approach

C. Schneider; D. Rönchen; C. Hanhart; Ulf-G. Meißner

doi:10.1140/epja/s10050-025-01719-x

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2024 Impact factor 2.8

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2025) 61: 241
https://doi.org/10.1140/epja/s10050-025-01719-x

Regular Article - Theoretical Physics

Coupled-channel contributions to the GDH sum rule from the Jülich–Bonn approach

C. Schneider¹^a, D. Rönchen¹, C. Hanhart¹ and Ulf-G. Meißner¹^,2^,3

¹ Institute for Advanced Simulation (IAS-4), Forschungszentrum Jülich, 52425, Jülich, Germany
² Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, 53115, Bonn, Germany
³ Peng Huanwu Collaborative Center for Research and Education, International Institute for Interdisciplinary and Frontiers, Beihang University, 100191, Beijing, China

^a c.schneider@fz-juelich.de

Received: 11 August 2025
Accepted: 9 October 2025
Published online: 27 October 2025

Abstract

We study the Gerasimov–Drell–Hearn (GDH) sum rule within a dynamical coupled-channel approach, the Jülich–Bonn model for light baryon resonances based on fits to an extensive data base of pion and photon induced data. Recently published photoproduction data for different observables with $π N$ $\pi N$ and $η N$ $\eta N$ final states are analyzed simultaneously with older data for the reactions $π N \to π N$ $\pi N\rightarrow \pi N$ , $η N$ $\eta N$ , $K Λ$ $K\Lambda$ , $K Σ$ $K\Sigma$ and $γ p \to π N$ $\gamma p\rightarrow \pi N$ , $η N$ $\eta N$ , $K Λ$ $K\Lambda$ , $K Σ$ $K\Sigma$ . The impact of the new data on the resonance spectrum is investigated and the contribution of the individual channels to the GDH integral is determined.

Communicated by Che-Ming Ko.

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