Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 26: Electromagnetic Probes IV, Electro-, Photoproduction
HK 26.7: Talk
Tuesday, March 17, 1998, 15:45–16:00, B
Measurement of the photon asymmetry for neutral pion production on the proton in the Δ(1232)–region* — •R. Leukel — Institut für Kernphysik, Universität Mainz, Johann–Joachim–Becher–Weg 45, D–55099 Mainz
The photon asymmetry for the reaction
γ→ + p → π0 + p in the
Δ–resonance–region allows to investigate the interference term
between the small electric quadrupole amplitude (E2) and the dominant
magnetic dipole amplitude (M1) of the N → Δ transition.
A precise experimental value for the E2/M1–ratio is an important test for
different nucleon–models, since it can be interpreted as a “deformation”
of the nucleon, the Δ(1232)–resonance or both.
The measurement has been performed with the tagged photon beam
(Glasgow–Tagger) of the 855 MeV cw electron accelerator MAMI (Mainz
Microtron). Coherent bremsstrahlung from a diamond radiator has been exploited
with a degree of linear photon polarisation of ≈50% in the
Δ–region. Using the photon spectrometer TAPS, comprising 504
individual BaF2–detectors, the neutral pion was identified by its
2γ–decay.
First results will be presented.
* supported by Deutsche Forschungsgemeinschaft (SFB 201)