40 research outputs found
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
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 -matrix elements of a reaction of the type . 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.
Photonuclear effect in heavy deformed nuclei
The theory of Raman scattering is extended to include electric-quadrupole radiation. The results obtained are used to compute the elastic and Raman scattering cross sections of heavy deformed nuclei. The dipole and quadrupole resonances are described by a previously developed theory which includes surface vibrations and rotations. The computed cross sections are compared with experimental data for all those nuclei where both absorption and scattering cross sections are available. Some discrepances still exist in certain details; however, the over-all agreement between theory and experiment is very good
The generalized Gerasimov-Drell-Hearn sum rule for deuteron electrodisintegration
The generalized Gerasimov-Drell-Hearn sum rule for
deuteron electrodisintegration as function of the squared
four-momentum transfer is evaluated by explicit integration. The
calculation is based on a conventional nonrelativistic framework using a
realistic -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,
mb, at low fm which is
almost exclusively driven by the nucleon isovector anomalous magnetic moment
contribution to the magnetic dipole transition to the -state. Above
fm the integral approaches zero
rapidly.Comment: 6 pages Revtex4, 4 figure
Influence of Coulomb distortion on polarization observables in elastic electromagnetic lepton hadron scattering at low energies
The formal expression for the most general polarization observable in elastic
electromagnetic lepton hadron scattering at low energies is derived for the
nonrelativistic regime. For the explicit evaluation the influence of Coulomb
distortion on various polarization observables is calculated in a distorted
wave Born approximation. Besides the hyperfine interaction also the spin-orbit
interactions of lepton and hadron are included. For like charges the Coulomb
repulsion reduces strongly the size of polarization observables compared to the
plane wave Born approximation whereas for opposite charges the Coulomb
attraction leads to a substantial increase of these observables for hadron lab
kinetic energies below about 20 keV.Comment: 32 pages, 26 figures. Typos corrected, notation slightly changed,
figures redrawn, one figure and references added. A condensed version is in
press in Physical Review
Inclusive electron scattering off 4He
Inclusive electron scattering off 4He is calculated exactly with a complete
treatment of the final state interaction within a simple semirealistic
potential model. We discuss results for both the longitudinal and the
transverse response functions, at various momentum transfers. A consistent
meson exchange current is implemented. Good agreement with available
experimental data is found for the longitudinal response function, while some
strength is still missing in the transverse response function.Comment: 4 pages, 3 figures. to appear in the proceedings of the 18th
International IUPAP Conference on Few-Body Problems in Physics,
Santos-S.Paulo, August 21-26, 200
Photon Scattering with the Lorentz Integral Transform Method
The application of the Lorentz integral transform (LIT) method to photon
scattering off nuclei is presented in general. As an example, elastic photon
scattering off the deuteron in the unretarded dipole approximation is
considered using the LIT method. The inversion of the integral transform is
discussed in detail paying particular attention to the high-energy
contributions in the resonance term. The obtained E1-polarizabilities are
compared to results from the literature. The corresponding theoretical cross
section is confronted with experimental results confirming, as already known
from previous studies, that the E1-contribution is the most important one at
lower energies.Comment: 15 pages, 10 figure
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 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 and 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 and degrees of freedom, a
reasonable fit to experimental -scattering data could be achieved.Comment: 30 pages revtex including 17 figures, outline of model and discussion
shortened, typos correcte