22 research outputs found
Production of three-body Efimov molecules in an optical lattice
We study the possibility of associating meta-stable Efimov trimers from three
free Bose atoms in a tight trap realised, for instance, via an optical lattice
site or a microchip. The suggested scheme for the production of these molecules
is based on magnetically tunable Feshbach resonances and takes advantage of the
Efimov effect in three-body energy spectra. Our predictions on the energy
levels and wave functions of three pairwise interacting 85Rb atoms rely upon
exact solutions of the Faddeev equations and include the tightly confining
potential of an isotropic harmonic atom trap. The magnetic field dependence of
these energy levels indicates that it is the lowest energetic Efimov trimer
state that can be associated in an adiabatic sweep of the field strength. We
show that the binding energies and spatial extents of the trimer molecules
produced are comparable, in their magnitudes, to those of the associated
diatomic Feshbach molecule. The three-body molecular state follows Efimov's
scenario when the pairwise attraction of the atoms is strengthened by tuning
the magnetic field strength.Comment: 21 pages, 8 figures (final version
Comparison of Relativistic Nucleon-Nucleon Interactions
We investigate the difference between those relativistic models based on
interpreting a realistic nucleon-nucleon interaction as a perturbation of the
square of a relativistic mass operator and those models that use the method of
Kamada and Gl\"ockle to construct an equivalent interaction to add to the
relativistic mass operator. Although both models reproduce the phase shifts and
binding energy of the corresponding non-relativistic model, they are not
scattering equivalent. The example of elastic electron-deuteron scattering in
the one-photon-exchange approximation is used to study the sensitivity of
three-body observables to these choices. Our conclusion is that the differences
in the predictions of the two models can be understood in terms of the
different ways in which the relativistic and non-relativistic -matrices are
related. We argue that the mass squared method is consistent with conventional
procedures used to fit the Lorentz-invariant cross section as a function of the
laboratory energy.Comment: Revtex 13 pages, 5 figures, corrected some typo
Self-consistent Green's function method for nuclei and nuclear matter
Recent results obtained by applying the method of self-consistent Green's
functions to nuclei and nuclear matter are reviewed. Particular attention is
given to the description of experimental data obtained from the (e,e'p) and
(e,e'2N) reactions that determine one and two-nucleon removal probabilities in
nuclei since the corresponding amplitudes are directly related to the imaginary
parts of the single-particle and two-particle propagators. For this reason and
the fact that these amplitudes can now be calculated with the inclusion of all
the relevant physical processes, it is useful to explore the efficacy of the
method of self-consistent Green's functions in describing these experimental
data. Results for both finite nuclei and nuclear matter are discussed with
particular emphasis on clarifying the role of short-range correlations in
determining various experimental quantities. The important role of long-range
correlations in determining the structure of low-energy correlations is also
documented. For a complete understanding of nuclear phenomena it is therefore
essential to include both types of physical correlations. We demonstrate that
recent experimental results for these reactions combined with the reported
theoretical calculations yield a very clear understanding of the properties of
{\em all} protons in the nucleus. We propose that this knowledge of the
properties of constituent fermions in a correlated many-body system is a unique
feature of nuclear physics.Comment: 110 pages, accepted for publication on Prog. Part. Nucl. Phy
Close-to-threshold Meson Production in Hadronic Interactions
Studies of meson production at threshold in the hadron--hadron interaction
began in the fifties when sufficient energies of accelerated protons were
available. A strong interdependence between developments in accelerator
physics, detector performance and theoretical understanding led to a unique
vivid field of physics. Early experiments performed with bubble chambers
revealed already typical ingredients of threshold studies, which were
superseded by more complete meson production investigations at the nucleon beam
facilities TRIUMF, LAMPF, PSI, LEAR and SATURNE. Currently, with the advent of
the new cooler rings as IUCF, CELSIUS and COSY the field is entering a new
domain of precision and the next step of further progress.
The analysis of this new data in the short range limit permits a more
fundamental consideration and a quantitative comparison of the production
processes for different mesons in the few--body final states. The
interpretation of the data take advantage of the fact that production reactions
close-to-threshold are characterized by only a few degrees of freedom between a
well defined combination of initial and exit channels. Deviations from
predictions of phase-space controlled one-meson-exchange models are indications
of new and exciting physics. Precision data on differential cross sections,
isospin and spin observables -- partly but by no means adequately available --
are presently turning up on the horizon. There is work for the next years and
excitement of the physics expected. Here we try to give a brief and at the same
time comprehensive overview of this field of hadronic threshold production
studies.Comment: 100 pages, Review article to be published in Prog. Part. Nucl. Phys.
Vol. 49, issue 1 (2002
Faddeev description of two-hole–one-particle motion and the single-particle spectral function
Investigation of the Exclusive ^{3}He(e,e'pn)p Reaction
Cross sections for the ^{3}He(e,e'pn)p reaction were measured for the first
time at energy transfers of 220 and 270 MeV for several momentum transfers
ranging from 300 to 450 MeV/c. Cross sections are presented as a function of
the momentum of the recoil proton and the momentum transfer. Continuum Faddeev
calculations using the Argonne V18 and Bonn-B nucleon-nucleon potentials
overestimate the measured cross sections by a factor 5 at low recoil proton
momentum with the discrepancy becoming much smaller at higher recoil momentum.Comment: 5, pages, 3 figure
The Transverse Asymmetry from Quasi-elastic Process and the Neutron Magnetic Form Factor
We have measured the transverse asymmetry from inclusive scattering of
longitudinally polarized electrons from polarized 3He nuclei at quasi-elastic
kinematics in Hall A at Jefferson Lab with high statistical and systematic
precision. The neutron magnetic form factor was extracted based on Faddeev
calculations with an experimental uncertainty of less than 2 %.Comment: 4 pages, 2 figures, revtex, accepted for publication in PR
Precision Measurement of the Spin-dependent Asymmetry in the Threshold Region of
We present the first precision measurement of the spin-dependent asymmetry in
the threshold region of at -values of 0.1 and
0.2 (GeV/c). The agreement between the data and non-relativistic Faddeev
calculations which include both final-state interactions (FSI) and
meson-exchange currents (MEC) effects is very good at = 0.1 (GeV/c),
while a small discrepancy at = 0.2 (GeV/c) is observed.Comment: 5 pages, 2 figures, 2 tables. To appear in Phys. Rev. Let