On Complete Sets of Polarization Observables

A new criterion is developed which provides a check as to whether a chosen set of polarization observables is complete with respect to the determination of all independent $T$-matrix elements of a reaction of the type $a+b\to c+d+...$. As an illustrative example, this criterion is applied to the longitudinal observables of deuteron electrodisintegration.Comment: 8 pages revtex, final version, accepted for Nucl. Phys.

General Survey of Polarization Observables in Deuteron Electrodisintegration

Polarization observables in inclusive and exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target are systematically surveyed using the standard nonrelativistic framework of nuclear theory but with leading order relativistic contributions included. The structure functions and the asymmetries corresponding to the various nucleon polarization components are studied in a variety of kinematic regions with respect to their sensitivity to realistic $NN$-potential models, to subnuclear degrees of freedom in terms of meson exchange currents, isobar configurations and to relativistic effects in different kinematical regions, serving as a benchmark for a test of present standard nuclear theory with effective degrees of freedom.Comment: 56 pages, 32 figures, revtex

The generalized Gerasimov-Drell-Hearn sum rule for deuteron electrodisintegration

The generalized Gerasimov-Drell-Hearn sum rule $I^{GDH}_{\gamma^*d}(Q^2)$ for deuteron electrodisintegration $d(e,e')np$ as function of the squared four-momentum transfer $Q^2$ is evaluated by explicit integration. The calculation is based on a conventional nonrelativistic framework using a realistic $NN$-potential and including contributions from meson exchange currents, isobar configurations and leading order relativistic terms. Good convergence is achieved. The prominent feature is a deep negative minimum, $I_{\gamma^* d}^{GDH}=-9.5$ mb, at low $Q^2\approx 0.2$ fm$^{-2}$ which is almost exclusively driven by the nucleon isovector anomalous magnetic moment contribution to the magnetic dipole transition to the $^1S_0$-state. Above $Q^2=20$ fm$^{-2}$ the integral $I^{GDH}_{\gamma^*}(Q^2)$ approaches zero rapidly.Comment: 6 pages Revtex4, 4 figure

Hadron Structure Studied with the Electromagnetic Probe - from Giant Resonances to Meson Production

The development of theoretical photonuclear physics over the last 40 years is illustrated by a few selected examples highlighting a number of important issues like collective motion in nuclei, the role of subnuclear degrees of freedom, relativity and meson production.Comment: 10 pages latex including 10 figures, invited talk presented at the Symposium on Fundamental Issues in Elementary Matter, Sept. 25-29, 2000, Bad Honnef, German

The Role of Meson Retardation in the NN Interaction above Pion Threshold

A model is developed for the hadronic interaction in the two-nucleon system above pion threshold which is based on meson, nucleon and $\Delta$ degrees of freedom and which includes full meson retardation in the exchange operators. For technical reasons, the model allows maximal one meson to be present explicitly. Thus the Hilbert space contains besides $NN$ and $N\Delta$ also configurations consisting of two nucleons and one meson. For this reason, only two- and three-body unitarity is obeyed, and the model is suited for reactions in the two nucleon sector only, where one pion is produced or absorbed. Starting from a realistic pure nucleonic retarded potential, which had to be renormalized because of the additional $\pi$ and $\Delta$ degrees of freedom, a reasonable fit to experimental $NN$-scattering data could be achieved.Comment: 30 pages revtex including 17 figures, outline of model and discussion shortened, typos correcte

Spin asymmetry and GDH sum rule for real and virtual photons for the deuteron

An explicit evaluation of the spin asymmetry of the deuteron and the associated GDH sum rule is presented which includes disintegration, single and double pion and eta production. For the GDH integral a large cancellation is found between the disintegration channel and the meson production channels. Furthermore, first results for the contribution of the disintegration channel to the generalized GDH integral at constant four-momentum transfer reveal a dominance of the isovector M1 transition to the $^1$S$_0$-state near threshold resulting in a negative contribution with a minimum around $Q^2\approx 0.2$ fm$^{-2}$ which is driven by the nucleon anomalous isovector magnetic moment.Comment: 9 pages, 7 figures, World Scientific style, invited talk at GDH 2004 Symposiu

On the Gerasimov-Drell-Hearn sum rule for the deuteron

The Gerasimov-Drell-Hearn sum rule is evaluated for the deuteron by explicit integration up to 550 MeV including contributions from the photodisintegration channel and from coherent and incoherent single pion production as well. The photodisintegration channel converges fast enough in this energy range and gives a large negative contribution, essentially from the $^1S_0$ resonant state near threshold. Its absolute value is about the same size as the sum of proton and neutron GDH values. It is only partially cancelled by the single pion production contribution. But the incoherent channel has not reached convergence at 550 MeV.Comment: 6 pages latex including 3 postscript figures, talk at the 15th Int. Conf. on Few-Body Problems in Physics, Groningen, Netherlands, 22-26 July 1997. To be published in Nucl. Phys.