The aim of the proposed experiment is to determine the values of proton electric and magnetic polarizabilities with a precision of about 0.5%. This aim can be reached by measurements of the energy dependence of the cross section for g
p elastic scattering with a statistical accuracy better than 1% at the photon energy of 20-100 MeV for selected scattering angles (q
scat=90o and 130o are proposed). The measurement can be performed using an untagged bremsstrahlung photon beam of »
100 MeV energy and of a few m
A current. The scattered photons will be detected with a large NaI g
-spectrometer with a solid angle for detection of 0.025 sr. In order to reduce background, the recoil protons will be detected with a dedicated high-pressure hydrogen-filled ionization chamber which will serve as both the target and the recoil proton detector.
The proposed experimental method is also suitable for measuring the electric and magnetic neutron polarizabilities with high accuracy by performing a similar experiment with the deuteron target.
A high-pressure hydrogen-filled ionization chamber to register recoil protons has been fabricated at PNPI, and the whole experimental setup to carry out the discussed measurements has been built at the Technical University in Darmstadt (TUD) and successfully tested. However, due to problems with the TUD electron accelerator the data taking has not been performed.
A possibility to perform such an experiment at the Mainz electron accelerator is under consideration.
(For more detail review see article "COMPTON SCATTERING ON PROTONS BELOW PION THRESHOLD: MEASUREMENT OF ELECTRIC AND MAGNETIC POLARIZABILITIES OF PROTON (PROJECT)" in PNPI HEPD Report "Main Scientific Activities 1997-2001").
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