2,572 research outputs found
Semi-realistic nucleon-nucleon interactions with improved neutron-matter properties
New parameter-sets of the semi-realistic nucleon-nucleon interaction are
developed, by modifying the M3Y interaction but maintaining the tensor channels
and the longest-range central channels. The modification is made so as to
reproduce microscopic results of neutron-matter energies, in addition to the
measured binding energies of doubly magic nuclei including Sn and the
even-odd mass differences of the Z=50 and N=82 nuclei in the self-consistent
mean-field calculations. Separation energies of the proton- or neutron-magic
nuclei are shown to be in fair agreement with the experimental data. With the
new parameter-sets M3Y-P6 and P7, the isotropic spin-saturated symmetric
nuclear matter remains stable in the density range as wide as , while keeping desirable results of the previous parameter-set on
finite nuclei. Isotope shifts of the Pb nuclei and tensor-force effects on
shell structure are discussed.Comment: 18 pages including 7 figure
Monoenergetic Neutrino Beam for Long Baseline Experiments
In an electron capture process by a nucleus, emitted neutrinos are
monoenergetic. By making use of it, we study how to get a completely
monoenergetic neutrino beam in a long baseline experiment.Comment: 9 pages, no figure, som typos are corrected, e.g. equation number
quoted in table I is correcte
SeaWiFS technical report series. Volume 6: SeaWiFS technical report series cumulative index: Volumes 1-5
The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is the follow-on ocean color instrument to the Coastal Zone Color Scanner (CZCS), which ceased operations in 1986, after an eight year mission. SeaWiFS is expected to be launched in August 1993, on the Sea Star satellite, being built by Orbital Sciences Corporation (OSC). The SeaWiFS Project at the NASA/Goddard Space Flight Center (GSFC) has undertaken the responsibility of documenting all aspects of this mission, which is critical to the ocean color and marine science communities. This documentation, entitled the SeaWiFS Technical Report Series, is in the form of NASA Technical Memoranda Number 104566. All reports published are volumes within the series. This volume serves as a reference, or guidebook, to the previous five volumes and consists of four main sections including an index to key words and phrases, a list of all references cited, and lists of acronyms and symbols used. It is our intention to publish a summary index of this type after every five volumes in the series. This will cover the topics published in all previous editions of the indices, that is, each new index will include all of the information contained in the preceding indices
SeaWiFS Technical Report Series. Volume 7: Cloud screening for polar orbiting visible and infrared (IR) satellite sensors
Methods for detecting and screening cloud contamination from satellite derived visible and infrared data are reviewed in this document. The methods are applicable to past, present, and future polar orbiting satellite radiometers. Such instruments include the Coastal Zone Color Scanner (CZCS), operational from 1978 through 1986; the Advanced Very High Resolution Radiometer (AVHRR); the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), scheduled for launch in August 1993; and the Moderate Resolution Imaging Spectrometer (IMODIS). Constant threshold methods are the least demanding computationally, and often provide adequate results. An improvement to these methods are the least demanding computationally, and often provide adequate results. An improvement to these methods is to determine the thresholds dynamically by adjusting them according to the areal and temporal distributions of the surrounding pixels. Spatial coherence methods set thresholds based on the expected spatial variability of the data. Other statistically derived methods and various combinations of basic methods are also reviewed. The complexity of the methods is ultimately limited by the computing resources. Finally, some criteria for evaluating cloud screening methods are discussed
Shell structure in neutron-rich Ca and Ni nuclei under semi-realistic mean fields
Shell structure in the neutron-rich Ca and Ni nuclei is investigated by the
spherical Hartree-Fock calculations with the semi-realistic interactions.
Specific ingredients of the effective interaction, particularly the tensor
force, often play a key role in the dependence of the neutron shell
structure. Such examples are found in N=32 and N=40; N=32 becomes magic or
submagic in Ca while its magicity is broken in Ni, and N=40 is
submagic (though not magic) in Ni but not in Ca. Comments are
given on the doubly magic nature of Ni. We point out that the loose
binding can lead to a submagic number N=58 in Ni, assisted by the weak
pair coupling.Comment: 14 pages including 5 figures, to appear in Physical Review C (Rapid
Communication
Model-independent Limits from Spin-dependent WIMP Dark Matter Experiments
Spin-dependent WIMP searches have traditionally presented results within an
odd group approximation and by suppressing one of the spin-dependent
interaction cross sections. We here elaborate on a model-independent analysis
in which spin-dependent interactions with both protons and neutrons are
simultaneously considered. Within this approach, equivalent current limits on
the WIMP-nucleon interaction at WIMP mass of 50 GeV/c are either
pb, pb or ,
depending on the choice of cross section or coupling strength
representation. These limits become less restrictive for either larger or
smaller masses; they are less restrictive than those from the traditional odd
group approximation regardless of WIMP mass. Combination of experimental
results are seen to produce significantly more restrictive limits than those
obtained from any single experiment. Experiments traditionally considered
spin-independent are moreover found to severely limit the spin-dependent phase
space. The extension of this analysis to the case of positive signal
experiments is explored.Comment: 12 pages, 12 figures, submitted to Phys. Rev.
Solution of two-center time-dependent Dirac equation in spherical coordinates: Application of the multipole expansion of the electron-nuclei interaction
A non-perturbative approach to the solution of the time-dependent, two-center
Dirac equation is presented with a special emphasis on the proper treatment of
the potential of the nuclei. In order to account for the full multipole
expansion of this potential, we express eigenfunctions of the two-center
Hamiltonian in terms of well-known solutions of the "monopole" problem that
employs solely the spherically-symmetric part of the interaction. When combined
with the coupled-channel method, such a wavefunction-expansion technique allows
for an accurate description of the electron dynamics in the field of moving
ions for a wide range of internuclear distances. To illustrate the
applicability of the proposed approach, the probabilities of the K- as well as
L- shell ionization of hydrogen-like ions in the course of nuclear alpha-decay
and slow ion-ion collisions have been calculated
GADZOOKS! Antineutrino Spectroscopy with Large Water Cerenkov Detectors
We propose modifying large water \v{C}erenkov detectors by the addition of
0.2% gadolinium trichloride, which is highly soluble, newly inexpensive, and
transparent in solution. Since Gd has an enormous cross section for radiative
neutron capture, with MeV, this would make neutrons visible
for the first time in such detectors, allowing antineutrino tagging by the
coincidence detection reaction (similarly for
). Taking Super-Kamiokande as a working example, dramatic
consequences for reactor neutrino measurements, first observation of the
diffuse supernova neutrino background, Galactic supernova detection, and other
topics are discussed.Comment: 4 pages, 1 figure, submitted to Phys. Rev. Lett. Correspondence to
[email protected], [email protected]
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