Münster 2002 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 44: Theory VIII

HK 44.4: Talk

Thursday, March 14, 2002, 17:15–17:30, C

Dispersion Effects in Nucleon Polarisabilities — •Robert Hildebrandt, Harald Griesshammer, and Thomas Hemmert — Institute for Theoretical Physics (T39), TU Muenchen, Germany

The dynamical nucleon polarisabilities can be defined via a multipole expansion of the structure amplitudes in nucleon Compton scattering [1]. In contradistinction to the static polarisabilities, dynamical polarisabilities gauge the response of the internal degrees of freedom of a nucleon to an external, real photon field of arbitrary energy but definite multipolarity. Being energy dependent, they therefore contain additional information about dispersive effects induced by internal relaxation, baryon resonances or meson production thresholds of the nucleon.
We present the different diagrams contributing in leading order ChPT — i. e. on the one pion loop level — in theories with and without explicit Δ(1232) degrees of freedom [2]. We further compare our results with a dispersion relation analysis. Once two counter terms are fixed at the static values, we obtain excellent predictions even well above the pion mass.

Work supported in part by DFG and BMBF.

1) H. Grießhammer, T. Hemmert: nucl-th/0110006
2) T. R. Hemmert, H. W. Griesshammer, R. P. Hildebrandt: in preparation