Dresden 2013 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 14: Hadronenstruktur und -spektroskopie
HK 14.2: Vortrag
Montag, 4. März 2013, 17:15–17:30, WIL-C307
Measurement Of The Proton Spin Polarisabilities — •Duncan Middleton — Mt. Allison University, New Brunswick, Canada — Institut für Kernphysik, Universität Mainz, Germany
Nucleon polarisabilities are fundamental structure observables related to the nucleon’s internal dynamics. Although the two scalar polarisabilities, αE1 and βM1, are reasonably well understood for the proton, very few experiments have attempted to extract the spin polarisabilities and none have managed to separate all four. First attempts to extract all four of these spin polarisabilities independently have begun at MAMI with two measurements, the first of the beam asymmetry, Σ3, and the second of the beam-target asymmetry, Σ2x.
The measurements took place in the real photon hall of the A2 collaboration at the Mainzer Mikrotron, MAMI. The first measurement used a beam of circularly polarised photons which were incident upon a polarised Butanol target. The second measurement used linearly polarised photons which were incident upon a liquid hydrogen target. In both measurements the retarded electrons from the Bremsstrahlung process were detected in the Glasgow-Mainz photon tagging spectrometer. The scattered photons and ejected protons from the Compton reaction were detected in the Crystal Ball and TAPS detector systems which covered a solid angle of ∼96% of 4π steradians.
Preliminary experimental asymmetries will be presented compared to predictions of the Σ2x asymmetry as well as first results from the Σ3 measurement.