Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 61: Electromagnetic Probes VIII, Properties of Nucleon, Pion
HK 61.5: Talk
Thursday, March 19, 1998, 16:00–16:15, B
Dispersion theoretical analysis of the nucleon spin polarizabilities — •B. Pasquini1, D. Drechsel1, G. Krein1, A. Metz1, and M. Vanderhaeghen2 — 1Institut f"ur Kernphysik, Universit"at Mainz, Becherweg 45, D-55099 Mainz — 2CEA/Saclay, DAPHNIA-SPhN, F-91191 Gif-sur-Yvette Cedex, France
Below pion threshold the residual amplitude TR of real Compton scattering off the nucleon can be parametrized in terms of electromagnetic polarizabilities. While to second order in the frequency of the initial photon TR contains only the electric (α) and magnetic (β) polarizability, the third order contribution is given by four spin polarizabilities, γ1, γ2, γ3 and γ4 [1].
We have calculated the spin polarizabilities from pion photoproduction data using forward dispersion relations [2]. We present these results and compare them with different model calculations. Only recently, the first experiments for a direct measurement of the individual γi have been proposed. To guide these experiments we have investigated the sensitivity of various polarization observables on the spin polarizabilities.
[1] S. Ragusa, Phys. Rev. D47, 3757 (1993); Phys. Rev. D49, 3157 (1994).
[2] D. Drechsel, G. Krein, O. Hanstein, nucl-th/9710029.