897 research outputs found
On the possibility of generating a 4-neutron resonance with a {\boldmath } isospin 3-neutron force
We consider the theoretical possibility to generate a narrow resonance in the
four neutron system as suggested by a recent experimental result. To that end,
a phenomenological three neutron force is introduced, in addition to a
realistic interaction. We inquire what should be the strength of the
force in order to generate such a resonance. The reliability of the
three-neutron force in the channel is exmined, by analyzing its
consistency with the low-lying states of H, He and Li and the
scattering.
The {\it ab initio} solution of the Schr\"{o}dinger equation is obtained
using the complex scaling method with boundary conditions appropiate to the
four-body resonances. We find that in order to generate narrow resonant
states a remarkably attractive force in the channel is required.Comment: 11 pages, 11 figures, minor change, published version, to be
published in Physical Review
Conceptual design optimization study
The feasibility of applying multilevel functional decomposition and optimization techniques to conceptual design of advanced fighter aircraft was investigated. Applying the functional decomposition techniques to the conceptual design phase appears to be feasible. The initial implementation of the modified design process will optimize wing design variables. A hybrid approach, combining functional decomposition techniques for generation of aerodynamic and mass properties linear sensitivity derivatives with existing techniques for sizing mission performance and optimization, is proposed
Benchmark Test Calculation of a Four-Nucleon Bound State
In the past, several efficient methods have been developed to solve the
Schroedinger equation for four-nucleon bound states accurately. These are the
Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis
variational, the stochastic variational, the hyperspherical variational, the
Green's function Monte Carlo, the no-core shell model and the effective
interaction hyperspherical harmonic methods. In this article we compare the
energy eigenvalue results and some wave function properties using the realistic
AV8' NN interaction. The results of all schemes agree very well showing the
high accuracy of our present ability to calculate the four-nucleon bound state.Comment: 17 pages, 1 figure
Inclusive and exclusive photoproduction on the deuteron: - and -threshold phenomena
Inclusive and exclusive photoproduction on the deuteron are
investigated theoretically. Modern hyperon-nucleon forces and a recently
updated kaon photoproduction operator for the process are
used. Sizable effects of the hyperon-nucleon final state interaction are found
near the and thresholds in the inclusive reaction.
Angular distributions for the exclusive process show clear final state
interaction effects in certain kinematic regions. Precise data especially for
the inclusive process around the threshold would help to clarify
the strength and property of the interaction.Comment: 14 pages, 10 figure
A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model
We upgrade a SU_6 quark-model description for the nucleon-nucleon and
hyperon-nucleon interactions by improving the effective meson-exchange
potentials acting between quarks. For the scalar- and vector-meson exchanges,
the momentum-dependent higher-order term is incorporated to reduce the
attractive effect of the central interaction at higher energies. The
single-particle potentials of the nucleon and Lambda, predicted by the G-matrix
calculation, now have proper repulsive behavior in the momentum region q_1=5 -
20 fm^-1. A moderate contribution of the spin-orbit interaction from the
scalar-meson exchange is also included. As to the vector mesons, a dominant
contribution is the quadratic spin-orbit force generated from the rho-meson
exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up
to T_lab=350 MeV are greatly improved especially for the 3E states. The
low-energy observables of the nucleon-nucleon and the hyperon-nucleon
interactions are also reexamined. The isospin symmetry breaking and the Coulomb
effect are properly incorporated in the particle basis. The essential feature
of the Lambda N - Sigma N coupling is qualitatively similar to that obtained
from the previous models. The nuclear saturation properties and the
single-particle potentials of the nucleon, Lambda and Sigma are reexamined
through the G-matrix calculation. The single-particle potential of the Sigma
hyperon is weakly repulsive in symmetric nuclear matter. The single-particle
spin-orbit strength for the Lambda particle is very small, in comparison with
that of the nucleons, due to the strong antisymmetric spin-orbit force
generated from the Fermi-Breit interaction.Comment: Revtex v2.09, 69 pages with 25 figure
Four-Body Bound State Calculations in Three-Dimensional Approach
The four-body bound state with two-body interactions is formulated in
Three-Dimensional approach, a recently developed momentum space representation
which greatly simplifies the numerical calculations of few-body systems without
performing the partial wave decomposition. The obtained three-dimensional
Faddeev-Yakubovsky integral equations are solved with two-body potentials.
Results for four-body binding energies are in good agreement with achievements
of the other methods.Comment: 29 pages, 2 eps figures, 8 tables, REVTeX
Phenomenological Lambda-Nuclear Interactions
Variational Monte Carlo calculations for (ground and
excited states) and are performed to decipher information on
-nuclear interactions. Appropriate operatorial nuclear and
-nuclear correlations have been incorporated to minimize the
expectation values of the energies. We use the Argonne two-body
NN along with the Urbana IX three-body NNN interactions. The study demonstrates
that a large part of the splitting energy in () is
due to the three-body NN forces. hypernucleus is
analyzed using the {\it s}-shell results. binding to nuclear matter
is calculated within the variational framework using the
Fermi-Hypernetted-Chain technique. There is a need to correctly incorporate the
three-body NN correlations for binding to nuclear matter.Comment: 18 pages (TeX), 2 figure
What Does Free Space Lambda-Lambda Interaction Predict for Lambda-Lambda Hypernuclei?
Data on Lambda-Lambda hypernuclei provide a unique method to learn details on
the strangeness S =-2 sector of the baryon-baryon interaction. From the free
space Bonn-Julich potentials, determined from data on baryon-baryon scattering
in the S=0,-1 channels, we construct an interaction in the S =-2 sector to
describe the experimentally known Lambda-Lambda hypernuclei. After including
short--range (Jastrow) and RPA correlations, we find masses for these
Lambda-Lambda hypernuclei in a reasonable agreement with data, taking into
account theoretical and experimental uncertainties. Thus, we provide a natural
extension, at low energies, of the Bonn-Julich OBE potentials to the S =-2
channel.Comment: 4 pages, 2 figures, revtex4 style. Minor changes in conclusions.
References updated. Accepted in Phys. Rev. Let
Analyzing power for the proton elastic scattering from neutron-rich 6He nucleus
Vector analyzing power for the proton-6He elastic scattering at 71
MeV/nucleon has been measured for the first time, with a newly developed
polarized proton solid target working at low magnetic field of 0.09 T. The
results are found to be incompatible with a t-matrix folding model prediction.
Comparisons of the data with g-matrix folding analyses clearly show that the
vector analyzing power is sensitive to the nuclear structure model used in the
reaction analysis. The alpha-core distribution in 6He is suggested to be a
possible key to understand the nuclear structure sensitivity.Comment: 5 pages, 3 figures, accepted for publication as a Rapid Communication
in Physical Review
Strangeness nuclear physics: a critical review on selected topics
Selected topics in strangeness nuclear physics are critically reviewed. This
includes production, structure and weak decay of --Hypernuclei, the
nuclear interaction and the possible existence of bound
states in nuclei. Perspectives for future studies on these issues are also
outlined.Comment: 63 pages, 51 figures, accepted for publication on European Physical
Journal
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