Properties of the πη, η', σ, f0(980) and a0(980) mesons and their relevance for the polarizabilities of the nucleon

The signs and values of the two-photon couplings FMγγ of mesons (M) and their couplings gMNN to the nucleon as entering into the t-channel parts of the difference of the electromagnetic polarizabilities (α-β) and the backward angle spin polarizabilities γπ are determined. The excellent agreement achieved with the experimental polarizabilities of the proton makes it possible to make reliable predictions for the neutron. The results obtained are αn=13.4±1.0, βn=1.8±1.0 (10-4 fm3), and γ(n)π=57.6±1.8 (10-4 fm4). New empirical information on the flavor wave functions of the f0(980)- and the a0(980)-meson is obtained. (orig.)