14 research outputs found
Polarization degrees of freedom in two-nucleon knockout from finite nuclei
Polarization observables for the A(e,e'NN) and A(\gamma,NN) reactions are a
powerful tool to study nucleon-nucleon correlations in the nuclear medium. In
this paper, model calculations for the ^{4}He(e,e'pp),
^{16}O(\vec{e},e'\vec{p}p), ^{16}O(\vec{e},e' \vec{p}n) and
^{12}C(\vec{\gamma},\vec{p}N) reactions are presented. The sensitivity of the
differential cross sections and polarization observables to central and
spin-dependent nucleon-nucleon correlations is discussed.Comment: 12 pages, 10 (color) figures, Talk Presented at the the Fourth
Workshop on Electromagnetically Induced Two-Hadron Emission, Granada (Spain),
May 26-29, 199
Polarization observables in electronuclear two-nucleon knockout
Differential (e,e'pp) measurements are presently recognized as a way of
studying short-range correlations in finite nuclei. The ()
and () differential cross section and polarization
observables are studied in a microscopic model that accounts for the
short-range correlations, outgoing-nucleon distortions, meson-exchange and
-isobar currents. It is pointed out that polarization observables
represent an attractive alternative for absolute electronuclear two-nucleon
knockout measurements. In the polarization transfer for
(), the effect of central short-range correlations is
predicted to be large while at the same time the final-state interaction
effects are small.Comment: 8 pages, 4 figures, to be published in Physics Letters
Spin-dependent correlations and the semi-exclusive ^{16}O(e,e'p) reaction
The effect of central, tensor and spin-isospin nucleon-nucleon correlations
upon semi-exclusive ^{16}O(e,e'p) reactions is studied for Q^2 and Bjorken x
values in the range and 0.15
x 2. The fully unfactorized calculations are performed in
a framework that accounts not only for the dynamical coupling of virtual
photons to correlated nucleon pairs but also for meson-exchange and
-isobar currents. Tensor correlations are observed to produce
substantially larger amounts of semi-exclusive ^{16}O(e,e'p) strength than
central correlations do and are predominantly manifest in the proton-neutron
knockout channel. With the exception of the case, in all
kinematical situations studied the meson-exchange and isobar currents are a
strong source of A(e,e'p) strength at deep missing energies. This feature gives
the A(e,e'p) strength at deep missing energies a pronounced transverse
character.Comment: 14 pages, 6 figure
Polarization degrees of freedom in photoinduced two-nucleon knockout from finite nuclei
The polarization degrees of freedom in photoinduced two-nucleon knockout from
finite nuclei are studied. It is pointed out that they open good perspectives
to study the dynamics of dinucleons in the medium in detail. The ()
and () angular cross sections, photon asymmetries and outgoing
nucleon polarizations are calculated for the target nuclei O and
C and photonenergies ranging from 100 up to 500 MeV. It is investigated
to which degree the two-nucleon emission reaction is dominated by
photoabsorption on proton-neutron and proton-proton
pairs in the nuclear medium. The calculations demonstrate that dominance of
wave photoabsorption in the () channel does not necessarily imply
that the reaction mechanism is similar to what is observed in deuteron
photodisintegration.Comment: 27 pages, REVTeX 3.0 with epsf.sty, 11 figures in EPS forma
Meson and Isobar Degrees of Freedom in A() reactions at
The effect of meson and isobar degrees of freedom in A()
and A(e,e'n) is studied for four-momentum transfers Q^2 in the range between
0.2 and 0.8 (GeV/c)^2. The calculations are performed in a non-relativistic
framework with explicit (N,\Delta,\pi) degrees-of-freedom. For the whole range
of momentum transfers under investigation the relative effect of the
meson-exchange and isobar degrees of freedom is significant. At low missing
momenta and quasi-elastic conditions, a tendency to reduce the (e,e'p) and
(e,e'n) differential cross sections is noticed. The greatest sensitivity is
found in the interference structure functions and . The recoil
polarization observables, on the other hand, are moderately affected by the
meson-exchange and -isobar currents.Comment: 16 pages (Revtex) + 18 figures (eps file