Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45 degrees, 125 degrees, and 135 degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N)+beta(N)=17.4+/-3.7 and alpha(N)-beta(N)=6.4+/-2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p)-beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n)=8.8+/-2.4(total)+/-3.0(model) and beta(n)=6.5-/+2.4(total)-/+3.0(model), respectively.

Compton scattering by the proton has been measured over a wide range covering photon energies 250 MeVEγ 800 MeV and photon scattering angles 30 • θ lab γ 150 • , using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The previously existing data base on proton Compton scattering is greatly enlarged by more than 700 new data points. The new data are interpreted in terms of dispersion theory based on the SAID-SM99K parametrization of photo-meson amplitudes. It is found that two-pion exchange in the t-channel is needed for a description of the data in the second resonance region. The data are well represented if this channel is modeled by a single pole with the mass parameter mσ ≈ 600 MeV. The asymptotic part of the spin dependent amplitude is found to be well represented by π 0 -exchange in the t-channel. No indications of additional effects were found. Using the mass parameter mσ of the two-pion exchange determined from the second resonance region and using the new global average for the difference of the electric and magnetic polarizabilities of the proton, α − β = (10.5 ± 0.9stat+syst ± 0.7 model ) × 10 −4 fm 3 , as obtained from a recent experiment on proton Compton scattering below pion photoproduction threshold, a backward spin-polarizability of γπ = (−37.1 ± 0.6stat+syst ± 3.0 model ) × 10 −4 fm 4 has been determined from data of the first resonance region below 455 MeV. This value is in a good agreement with predictions of dispersion relations and chiral perturbation theory. From a subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to a E2/M1 multipole ratio of the p → ∆ radiative transition of EMR(340 MeV)= (−1.7±0.4stat+syst ±0.2 model )%. It was found that this number is dependent on the parameterization of photo-meson amplitudes. With the MAID2K parameterization an E2/M1 multipole ratio of EMR(340 MeV)= (−2.0 ± 0.4stat+syst ± 0.2 model )% is obtained.

Compton scattering by the proton has been measured over a wide range covering photon energies 250 MeV < ∼ E γ < ∼ 800 MeV and photon scattering angles 30 • < ∼ θ lab γ < ∼ 150 • , using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The data are in good agreement with the dispersion theory based on the SAID-SM99K parameterization of photo-meson amplitudes. From the subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to the multipole E2/M1 ratio EMR(340 MeV) = (−1.6 ± 0.4 stat+syst ± 0.2 model )%. From all data below 455 MeV the proton's backward spin polarizability was determined to be γ π = (−37.9 ± 0.6 stat+syst ± 3.5 model ) × 10 −4 fm 4 .

Differential cross sections for elastic scattering of photons have been measured for 40 Ca at energies of 58 and 74 MeV and for 16 O and 4 He at 61 MeV, in the angular range from 45 • to 150 • . Evidence is obtained that there are no significant in-medium modifications of the electromagnetic polarizabilities except for those originating from meson exchange currents.

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