45 research outputs found
The HeH Reaction with Full Final--State Interaction
An {\it ab initio} calculation of the HeH longitudinal
response is presented. The use of the integral transform method with a Lorentz
kernel has allowed to take into account the full four--body final state
interaction (FSI). The semirealistic nucleon-nucleon potential MTI--III and the
Coulomb force are the only ingredients of the calculation. The reliability of
the direct knock--out hypothesis is discussed both in parallel and in non
parallel kinematics. In the former case it is found that lower missing momenta
and higher momentum transfers are preferable to minimize effects beyond the
plane wave impulse approximation (PWIA). Also for non parallel kinematics the
role of antisymmetrization and final state interaction become very important
with increasing missing momentum, raising doubts about the possibility of
extracting momentum distributions and spectroscopic factors. The comparison
with experimental results in parallel kinematics, where the Rosenbluth
separation has been possible, is discussed.Comment: 17 pages, 5 figure
Photodisintegration of Three-Body Nuclei with Realistic 2N and 3N Forces
Total photonuclear absorption cross sections of H and He are studied
using realistic NN and NNN forces. Final state interactions are fully included.
Two NN potential models, the AV14 and the r-space Bonn-A potentials, are
considered. For the NNN forces the Urbana-VIII and Tucson-Melbourne models are
employed. We find the cross section to be sensitive to nuclear dynamics. Of
particular interest in this work is the effect which NNN forces have on the
cross section. The addition of NNN forces not only lowers the peak height but
increases the cross section beyond 70 MeV by roughly 15%. Cross sections are
computed using the Lorentz integral transform method.Comment: Results for Bonn potential with model Bonn rA instead of model rB.
The Bonn rB results contained a small inexactness. After the correction it
turned out that Bonn rA is more suited for our purpose because it leads to a
binding energy of 8.15 MeV (about 0.25 MeV more than Bonn rB). In addition
the results for the other realistic potentials models are improved at low
energies (HH expansion was not completely convergent for the low-energy
results). LaTeX, 8 pages, 4 ps figure
Method to solve integral equations of the first kind with an approximate input
Techniques are proposed for solving integral equations of the first kind with
an input known not precisely. The requirement that the solution sought for
includes a given number of maxima and minima is imposed. It is shown that when
the deviation of the approximate input from the true one is sufficiently small
and some additional conditions are fulfilled the method leads to an approximate
solution that is necessarily close to the true solution. No regularization is
required in the present approach. Requirements on features of the solution at
integration limits are also imposed. The problem is treated with the help of an
ansatz proposed for the derivative of the solution. The ansatz is the most
general one compatible with the above mentioned requirements. The techniques
are tested with exactly solvable examples. Inversions of the Lorentz, Stieltjes
and Laplace integral transforms are performed, and very satisfactory results
are obtained. The method is useful, in particular, for the calculation of
quantum-mechanical reaction amplitudes and inclusive spectra of
perturbation-induced reactions in the framework of the integral transform
approach.Comment: 28 pages, 1 figure; the presentation is somewhat improved; to be
published in Phys. Rev.
Incorporation of three-nucleon force in the effective interaction hyperspherical harmonic approach
It is shown how a bare three-nucleon force is incorporated into the formalism
of the effective interaction approach for hyperspherical harmonics. As a
practical example we calculate the ground state properties of 3H and 3He using
the Argonne V18 nucleon-nucleon potential and the Urbana IX three-nucleon
force. A very good convergence of binding energies and matter radii is
obtained. We also find a very good agreement of our results compared to other
high precision calculations.Comment: 17 pages, 3 figure
Improved (e,e') response functions at intermediate momentum transfers: the 3He case
A possibility of extending the applicability range of non-relativistic
calculations of electronuclear response functions in the quasielasic peak
region is studied. We show that adopting a particular model for determining the
kinematical inputs of the non-relativistic calculations can extend this range
considerably, almost eliminating the reference frame dependence of the results.
We also show that there exists one reference frame, where essentially the same
result can be obtained with no need of adopting the particular kinematical
model. The calculation is carried out with the Argonne V18 potential and the
Urbana IX three-nucleon interaction. A comparison of these improved
calculations with experimental data shows a very good agreement for the
quasielastic peak positions at 600, 700 MeV/c and for the peak heights
at the two lower --values, while for the peak height at MeV/c one
finds differences of about 20%.Comment: 10 pages, 4 figure
Total 4He Photoabsorption Cross Section Revisited: Correlated HH versus Effective Interaction HH
Two conceptually different hyperspherical harmonics expansions are used for
the calculation of the total 4He photoabsorption cross section. Besides the
well known method of CHH the recently introduced effective interaction approach
for the hyperspherical formalism is applied. Semi-realistic NN potentials are
employed and final state interaction is fully taken into account via the
Lorentz integral transform method. The results show that the effective
interaction leads to a very good convergence, while the correlation method
exhibits a less rapid convergence in the giant dipole resonance region. The
rather strong discrepancy with the experimental photodisintegration cross
sections is confirmed by the present calculations.Comment: LaTeX, 7 pages, 3 ps figure