448 research outputs found
Solution of the Faddeev-Yakubovsky equations using realistic NN and 3N interaction
We solve the Faddeev-Yakubovsky equations for 3N and 4N bound states based on
the most modern realistic nucleon-nucleon interactions. We include different
realistic 3N forces. It is shown that all 3N force models can remove the
underbinding of the triton and alpha-particle which one obtains with existing
NN interactions. The agreement of theoretical predictions and the experimental
binding energy is quite good and there is little room left for the action of
four-nucleon forces in the alpha-particle. The effect of 3N forces on the wave
function is investigated.Comment: 4 pages, to appear in the proceedings of the "European Few-Body
Conference", Evora 200
A New Look into the Partial Wave Decomposition of Three-Nucleon Forces
We demonstrate that the partial wave decomposition of three-nucleon forces
used up to now in momentum space has to be necessarily unstable at high partial
waves. This does not affect the applications performed up to now, which were
restricted to low partial waves. We present a new way to perform the partial
wave decomposition which is free of that defect. This is exemplified for the
most often used -exchange Tuscon-Melbourne three-nucleon force. For the
lower partial waves the results of the old method are reproduced.Comment: 38 pages in REVTeX, 4 figures in PiCTe
Benchmark Calculations for the Triton Binding Energy for Modern NN Forces and the pi-pi Exchange Three-Nucleon Force
We present high precision benchmark calculations for the triton binding
energy using the most recent, phase equivalent realistic nucleon-nucleon (NN)
potentials and the Tuscon-Melbourne pi-pi three-nucleon force (3NF). That 3NF
is included with partial waves up to a total two-body angular momentum of
j_max=6. It is shown that the inclusion of the 3NF slows down the convergence
in the partial waves and j_max=5 is needed in order to achieve converged
results within a few keV. We adjust the cut-off parameter Lambda in the form
factors of the Tuscon-Melbourne 3NF separately for the different NN potentials
to the triton binding energy. This provides a set of phenomenological
three-nucleon Hamiltonians which can be tested in three-nucleon scattering and
systems with A>3. A connection between the probability to find two nucleons at
short distances in the triton and the effect of that 3NF on the triton binding
energy is pointed out.Comment: 18 pages REVTeX, 3 figure
Proton polarizations in polarized 3He studied with the \vec{3He} (\vec{e},e' p)d and \vec{3He} (\vec{e},e' p)pn processes
We study within the Faddeev framework the \vec{3He} (\vec{e},e' p)d as well
as the \vec{3He} (\vec{e},e' p)pn and \vec{3He} (\vec{e},e' n)pp reactions in
order to extract information on the proton and neutron polarization in
polarized 3He. We achieve clear analytical insight for simplified dynamical
assumptions and define conditions for experimental access to important 3He
properties. In addition we point to the possibility to measure the
electromagnetic proton form factors in the process \vec{3He} (\vec{e},e' p)d
which would test the dynamical picture and put limits on medium corrections of
the form factors.Comment: 38 pages, 22 figure
On the usefulness of the spectral function concept
The usefulness of the spectral function S in the process 3He(e,e'N) has been
investigated in a kinematical regime constrained by the conditions that the
three-nucleon center-of-mass energy is less than 150 MeV and the magnitude of
the three-momentum transfer smaller than 600 MeV/c. Results based on a full
treatment of the final state interaction are compared to the spectral function
approximation. In the case of proton knockout in the direction of the photon
kinematical conditions have been identified where both response functions, RL
and RT, can be well approximated by S. These conditions occur for certain low
missing momenta and missing energies but not in all cases. So care is required.
In case of neutron knockout only RT is a candidate for an approximate treatment
by S. In the case of RL the concept of using S is not valid in the studied
kinematical regime. This does not exclude the possibility that beyond that
regime it might be useful. Possible applications using S for the extraction of
electromagnetic form factors of the nucleons are pointed out.Comment: 27 pages, 25 fugure
Theoretical predictions for extraction of GEn from semi-inclusive electron scattering on polarized 3He based on various nucleon-nucleon interactions
The process 3He(e,e'n) with polarized electrons and 3He in the initial state
is theoretically analyzed with the aim to search for sensitivity to the
electric form factor of the neutron, GEn. Faddeev calculations based on five
high precision nucleon-nucleon force models are employed and stability versus
exchange of the nucleon-nucleon forces is demonstrated.Comment: 7 pages, 3 Postscript figure
Modern NN Force Predictions for the Total ND Cross Section up to 300 MeV
For several modern nucleon-nucleon potentials state-of-the-art Faddeev
calculations are carried out for the total cross section between 10 and
300 MeV projectile energy and compared to new high precision measurements. The
agreement between theory and data is rather good, with exception at the higher
energies where a 10% discrepancy builds up. In addition the convergence of the
multiple scattering series incorporated in the Faddeev scheme is studied
numerically with the result, that rescattering corrections remain important.
Based on this multiple scattering series the high energy limit of the total
cross section is also investigated analytically. In contrast to the naive
expectation that the total cross section is the sum of the and
total cross sections we find additional effects resulting from the rescattering
processes, which have different signs and different behavior as function of the
energy. A shadowing effect in the high energy limit only occurs for energies
higher than 300 MeV. The expressions in the high energy limit have
qualitatively a similar behavior as the exactly calculated expressions, but can
be expected to be valid quantitatively only at much higher energies.Comment: 22 pages, 5 figure
Spin dependent momentum distributions of proton-deuteron clusters in 3He from electron scattering on polarized 3He: theoretical predictions
The process (or
) is studied theoretically in a
Faddeev treatment with the aim to have access to the spin-dependent momentum
distribution of clusters in polarized He. Final state
interactions and meson exchange currents turn out to have a strong influence in
the considered kinematical regime (below the pion threshold). This precludes
the direct access to the momentum distribution except for small deuteron
momenta. Nevertheless, the results for the longitudinal and transverse response
functions are interesting as they reflect our present day understanding of the
reaction mechanism and therefore data would be very useful.Comment: 16 pages, 9 figure
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