Quasi-free Compton scattering and the polarizabilities of the neutron

Differential cross-sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been measured using the Glasgow/Mainz photon tagging spectrometer at the Mainz MAMI accelerator together with the Mainz 48 cm O * 64 cm NaI(Tl) photon detector and the Gottingen SENECA recoil detector. The data cover photon energies ranging from 200 MeV to 400 MeV at theta /sub gamma //sup LAB/ = 136.2 degrees . Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron detection efficiency of the SENECA detector was measured via the reaction p( gamma , pi /sup +/n). The ""free"" proton Compton scattering cross-sections extracted from the bound proton data are in reasonable agreement with those for the free proton which gives confidence in the method to extract the differential cross-section for free scattering from quasi-free data. Differential cross-sections on the free neutron have been extracted and the difference of the electromagnetic polarizabilities of the neutron has been determined to be alpha /sub n/ - beta /sub n/ = 9.8 +or- 3.6(stat)/sub -1.1//sup +2.1/(syst) +or- 2.2(model) in units of 10/sup -4/ fm/sup 3/. In combination with the polarizability sum alpha /sub n/ + beta /sub n/ = 15.2 +or- 0.5 deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, alpha /sub n/ = 12.5 +or- 1.8(stat)/sub -0.6//sup +1.1/(syst) +or- 1.1(model) and beta /sub n/ = 2.7 -or+ 1.8(stat)/sub -1.1//sup +0.6/(syst) -or+ 1.1(model) are obtained. The backward spin polarizability of the neutron was determined to be gamma /sub pi //sup (n)/ = (58.6 +or- 4.0) * 10/sup -4/ fm/sup 4/