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HK: Physik der Hadronen und Kerne
HK 35: Plenary Session
HK 35.3: Plenary Talk
Thursday, March 14, 2002, 09:30–10:00, Plenarsaal
Experimental verification of the GDH sum rule at ELSA and MAMI — •Klaus Helbing — Erlangen: Universität Erlangen-Nürnberg, Physikalisches Institut, Abteilung IV, Erwin-Rommel-Str. 1, D-91058 Erlangen
The Gerasimov-Drell-Hearn (GDH) sum rule connects static properties of the nucleon like the anomalous magnetic moment κ and the nucleon mass m, with the helicity dependent photoabsorption cross sections σ3/2 and σ1/2, which are observables of the dynamics of the excitation spectrum.
|
| ⎡ ⎣ | σ3/2(ν)−σ1/2(ν) | ⎤ ⎦ | = |
| · κ2 |
For the first time this fundamental sum rule is verified experimentally with circularly polarized real photons and longitudinally polarized nucleons. First results of our measurements on the proton in the photon energy range 200-800 MeV at the Mainz electron accelerator MAMI have been published. The measurements of the GDH-Collaboration have been continued at the accelerator ELSA in Bonn where a tagged photon facility allows to study photon energies from 680 MeV up to 3 GeV. Our new data provide up to now unaccessible information about the spin structure of the proton from the resonance region up to the onset of the Regge regime.