Bonn 2010 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 52: Hadronenstruktur und -spektroskopie IX

HK 52.5: Vortrag

Donnerstag, 18. März 2010, 18:00–18:15, HG III

Photoproduction of π0-Mesons off Protons and Neutrons — •Manuel Dieterle — Department of Physics, University of Basel, Switzerland

The photoproduction of the lightest mesons, the pions, from the free proton was widely used as a tool to study the properties of the Δ(1232)-resonance. However, photoproduction from the free proton alone tells nothing about the isospin structure of the electromagnetic transitions, since this requires the investigation of the same reactions on the neutron. Since free neutron targets do not exist, one can only use photoproduction from light nuclei, in particular from the deuteron. Although the deuteron is only weakly bound, the production cross section will of course be influenced by nuclear Fermi motion and possibly also by nuclear final state interaction effects (FSI). Hence, to extract the elementary n(γ,x)n amplitudes, one at least needs knowledge of the off-shell behaviour of the nucleons inside the nucleus and to take final state interactions into account. Fortunately, such effects can be studied by a comparison of the quasi-free cross section measured in coincidence with recoil protons to the free proton cross section.

We will discuss results from a new high statistics measurement of π0- photoproduction off the deuteron in coincidence with recoil protons and neutrons throughout the second and third resonance regions. In addition, results obtained in parallel for the coherent d(γ,π0)d reaction give further input for the analysis of the isospin degree of freedom.

Supported by Swiss National Fund and DFG.

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