Abstract
The next generation of Compton scattering experiments is underway at Mainz and other laboratories, where the goal is precision measurements of the scalar and vector polarizabilities of the nucleon using polarized photons and polarized targets. Results are presented for the first double polarized Compton scattering experiment utilizing a polarized proton target. Preliminary results are presented for the four spin polarizabilities of the proton.
Highlights
Electromagnetic polarizabilities are fundamental properties of composite systems such as molecules, atoms, nuclei, and hadrons,[1] telling us about the response of a system when an external electromagnetic field is applied
This is close to an estimate for the electric field strength of a 100 MeV photon Compton scattering on the proton
Because the spin polarizability effect varies as ω3, the sensitivity to the spin polarizabilities, relative to that of α and β, is greatest in Compton scattering reactions in the ∆(1232) region, but below below the threshold for double-pion photoproduction where additional terms must be included
Summary
Electromagnetic polarizabilities are fundamental properties of composite systems such as molecules, atoms, nuclei, and hadrons,[1] telling us about the response of a system when an external electromagnetic field is applied. The electric field needed to induce a significant distortion of the proton should go as the characteristic energy level spacing in the proton, approximately 100 MeV, divided by the size of the proton, approximately 1 fm, approximately 1023 V/m. This is close to an estimate for the electric field strength of a 100 MeV photon Compton scattering on the proton. Extracted polarizabilities can provide a guide by favoring, or disfavoring, models of hadron structure and QCD. This is an Open Access article published by World Scientific Publishing Company. Because the spin polarizability effect varies as ω3, the sensitivity to the spin polarizabilities, relative to that of α and β, is greatest in Compton scattering reactions in the ∆(1232) region, but below below the threshold for double-pion photoproduction where additional terms must be included
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