Heidelberg 2015 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 8: Hadron Structure and Spectroscopy 1

HK 8.1: Gruppenbericht

Montag, 23. März 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, Σ_2x and Σ_2z, 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 Σ_2x and Σ_2z used a frozen-spin butanol target. The current results of these experiments as well as future plans will be discussed in this talk.