Heidelberg 2015 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 8: Hadron Structure and Spectroscopy 1
HK 8.1: Group Report
Monday, March 23, 2015, 14:30–15:00, T/SR19
Compton Scattering Asymmetries at MAMI to Extract Proton Polarizabilities — •Philippe Martel — Institut für Kernphysik, Universität Mainz, Mainz, Germany — Department of Physics, Mount Allison University, Sackville, Canada
The internal structure of the proton is described by various fundamental quantities such as the mass, charge, and anomalous magnetic moment. The proton scalar and spin polarizabilities appear at second and third order, respectively, in the energy expansion of the Compton scattering amplitude. While the scalar polarizabilities have previously been determined, albeit with large uncertainties, the spin polarizabilities have only been extracted in various linear combinations.
A Compton scattering program in the A2 Collaboration at MAMI has sought to extract these fundamental quantities through measurements of the beam asymmetry, Σ3, below either π0 or 2π0 production threshold, and two beam-target asymmetries, Σ2x and Σ2z, also below 2π0 production threshold. All of the experiments made use of the Crystal Ball and TAPS detectors, while Σ3 used a liquid hydrogen target and both Σ2x and Σ2z used a frozen-spin butanol target. The current results of these experiments as well as future plans will be discussed in this talk.