126 research outputs found
Polarization phenomena in hyperon-nucleon scattering
We investigate polarization observables in hyperon-nucleon scattering by
decomposing scattering amplitudes into spin-space tensors, where each component
describes scattering by corresponding spin-dependent interactions, so that
contributions of the interactions in the observables are individually
identified. In this way, for elastic scattering we find some linear
combinations of the observables sensitive to particular spin-dependent
interactions such as symmetric spin-orbit (LS) interactions and antisymmetric
LS ones. These will be useful to criticize theoretical predictions of the
interactions when the relevant observables are measured. We treat vector
analyzing powers, depolarizations, and coefficients of polarization transfers
and spin correlations, a part of which is numerically examined in scattering as an example. Total cross sections are studied for polarized
beams and targets as well as for unpolarized ones to investigate spin
dependence of imaginary parts of forward scattering amplitudes.Comment: 15 pages, 8 figure
Central and tensor components of three-nucleon forces in low-energy proton-deuteron scattering
Contributions of three-nucleon forces (3NF) to proton-deuteron scattering
observables at energies below the deuteron breakup threshold are studied by
solving the Faddeev equation that includes the Coulomb interaction. At E_p=3.0
MeV, we find that the central part of a two-pion exchange 3NF removes the
discrepancy between measured cross sections and the calculated ones by
two-nucleon forces, and improves the agreement with T_{22} experimental data.
However, the tensor part of the 3NF fails in reproducing data of the analyzing
power T_{21} by giving worse agreement between the measured and the calculated.
Detailed examinations of scattering amplitudes suggest that a P-wave
contribution in spin quartet tensor amplitudes has unsuitable sign for
reproducing the T_{21} data.Comment: 6 pages, 6 figure
Fine-Scale Spatial Organization of Face and Object Selectivity in the Temporal Lobe: Do Functional Magnetic Resonance Imaging, Optical Imaging, and Electrophysiology Agree?
The spatial organization of the brain's object and face representations in the temporal lobe is critical for understanding high-level vision and cognition but is poorly understood. Recently, exciting progress has been made using advanced imaging and physiology methods in humans and nonhuman primates, and the combination of such methods may be particularly powerful. Studies applying these methods help us to understand how neuronal activity, optical imaging, and functional magnetic resonance imaging signals are related within the temporal lobe, and to uncover the fine-grained and large-scale spatial organization of object and face representations in the primate brain
Spin observables in nucleon-deuteron scattering and three-nucleon forces
Three-nucleon forces, which compose an up-to-date subject in few-nucleon systems, provide a good account of the triton binding energy and the cross section minimum in proton-deuteron elastic scattering. However, three-nucleon forces do not explain spin observables such as the nucleon and deuteron analyzing powers, suggesting serious defects in their spin dependence. We study the spin structure of nucleon-deuteron elastic amplitudes by decomposing them into spin-space tensors and examine effects of three-nucleon forces to each component of the amplitudes obtained by solving the Faddeev equation. Assuming that the spin-scalar amplitudes dominate the others, we derive simple expressions for spin observables in the nucleon-deuteron elastic scattering. The expressions suggest that a particular combination of spin observables in the scattering provides direct information on scalar, vector, or tensor component of the three-nucleon forces. These effects are numerically investigated by the Faddeev calculation
Complete set of total cross sections for imaginary parts of nd forward scattering amplitudes, and three-nucleon force effects
In neutron-deuteron scattering, four total cross sections are shown to form a complete set for the determinationof the imaginary parts of the forward amplitudes by means of the optical theorem. The amplitudes aredecomposed into scalar and tensor components in spin space. Contributions of three-nucleon forces ~3NF! tothese amplitudes are studied by Faddeev calculations. Significant effects of the 3NF on the tensor componentsare predicted
Relationships among depolarizations in scattering of polarized protons from 3He at intermediate energies
We derive relation formulas for proton depolarizations in proton-3He (p-3He) elastic scattering in a form that makes it easy to identify contributions of spin-dependent interactions. The formulas explain approximate relations found in the depolarizations measured at Ep=800 MeV when the magnitudes of scattering amplitudes due to p-3He spin?spin and tensor interactions are small. This nature of the interactions is investigated from the viewpoint of folding models. It is shown that the spin?spin and tensor interactions are significantly diminished owing to characteristics of nucleon densities of 3He, which are calculated from a solution of the Faddeev equation. A folding model calculation with the densities and a simple nuclear potential shows that the p-3He spin?spin interaction is much weaker than the spin-independent central interaction
Polarization phenomena in hyperon-nucleon scattering
We investigate polarization observables in hyperon-nucleon scattering by decomposing scattering amplitudes into spin-space tensors, where each component describes scattering by corresponding spin-dependent interactions, so that contributions of the interactions in the observables are individually identified. In this way, for elastic scattering we find some linear combinations of the observables sensitive to particular spin-dependent interactions such as symmetric spin-orbit (LS) interactions and antisymmetric LS ones. These will be useful to criticize theoretical predictions of the interactions when the relevant observables are measured. We treat vector analyzing powers, depolarizations, and coefficients of polarization transfers and spin correlations, a part of which is numerically examined in +p scattering as an example. Total cross sections are studied for polarized beams and targets as well as for unpolarized ones to investigate spin dependence of imaginary parts of forward scattering amplitudes
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
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