389 research outputs found
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.
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 -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 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
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
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 S-state near threshold
resulting in a negative contribution with a minimum around
fm which is driven by the nucleon anomalous isovector magnetic moment.Comment: 9 pages, 7 figures, World Scientific style, invited talk at GDH 2004
Symposiu
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
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 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.
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