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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 Ø × 64 cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. The data cover photon energies ranging from 200 MeV to 400 MeV at θ LAB γ = 136.2 • . 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(γ, π + 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 αn − βn = 9.8 ± 3.6(stat) +2.1 −1.1 (syst) ± 2.2(model) in units of 10 −4 fm 3 . In combination with the polarizability sum αn + βn = 15.2 ± 0.5 deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, αn = 12.5 ± 1.8(stat) +1.1 −0.6 (syst) ± 1.1(model) and βn = 2.7 ∓ 1.8(stat) +0.6 −1.1 (syst) ∓ 1.1(model) are obtained. The backward spin polarizability of the neutron was determined to be γ (n) π = (58.6 ± 4.0) × 10 −4 fm 4 . PACS. 13.60.Fz Compton scattering -14.20.Dh Protons and neutrons -25.20.Dc Photon absorption and scattering ⋆ Supported by Deutsche Forschungsgemeinschaft (SFB 201, SFB 443, Schwerpunktprogramm 1034 through contracts DFG-Wi1198 and DFG-Schu222), and by the German Russian exchange program 436 RUS 113/510.) a Part of the Doctoral Thesis b Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig c Part of the Doctoral Thesis d Part of the Habilitation Thesistomary to consider special properties of these amplitudes which have a transparent physical interpretation. These properties are given in terms of electromagnetic structure constants of which the E2/M1 ratio of the p → ∆ transition, the electric and magnetic polarizabilities α and β, respectively, and the spin polarizabilities γ 0 and γ π , for the forward and backward direction, respectively, are the most prominent.These electromagnetic structure constants have been studied for the proton for a long time, whereas the corresponding investigations for the neutron are only beginning. This contrasts with the fact that for their interpretation it is of great interest to know whether or not the proton and the neutron have the same or different electromagnetic structure constants. This is one reason to study the electromagnetic polarizabilities of the neutron in addition to those for the proton. Since Compton scattering

Measuring Compton scattered photons and recoil neutrons in coincidence, quasifree Compton scattering by the neutron has been investigated at MAMI (Mainz) at theta(lab)(gamma) = 136 degrees in an energy range from 200 to 400 MeV. From the data a polarizability difference of alpha(n)-beta(n) = 9.8+/-3.6(stat)+2.1-1.1(syst)+/-2.2(model) in units of 10(-4) fm(3) has been determined. In combination with the polarizability sum alpha(n)+beta(n) = 15.2+/-0.5 deduced from photoabsorption data, the first precise results for the neutron electric and magnetic polarizabilities, alpha(n) = 12.5+/-1.8(stat)+1.1-0.6(syst)+/-1.1(model) and beta(n) = 2.7-/+1.8(stat)+0.6-1.1(syst)-/+1.1(model), are obtained.

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