1,141 research outputs found
The surface diffuseness and the spin-orbital splitting in relativistic continuum Hartree-Bogoliubov theory
The Relativistic Continuum Hartree Bogoliubov theory (RCHB), which is the
extension of the Relativistic Mean Field and the Bogoliubov transformation in
the coordinate representation, has been used to study tin isotopes. The pairing
correlation is taken into account by a density-dependent force of zero range.
RCHB is used to describe the even-even tin isotopes all the way from the proton
drip line to the neutron drip line. The contribution of the continuum which is
important for nuclei near the drip-line has been taken into account. The
theoretical as well as the neutron, proton, and matter radii are
presented and compared with the experimental values where they exist. The
change of the potential surface with the neutron number has been investigated.
The diffuseness of the potentials in tin isotopes is analyzed through the
spin-orbital splitting in order to provide new way to understand the halo
phenomena in exotic nuclei. The systematic of the isospin and energy dependence
of these results are extracted and analyzed.Comment: 11 figure
Microscopic multicluster description of neutron-halo nuclei with a stochastic variational method
To test a multicluster approach for halo nuclei, we give a unified
description for the ground states of He and He in a model comprising an
cluster and single-neutron clusters. The intercluster wave function is
taken a superposition of terms belonging to different arrangements, each
defined by a set of Jacobi coordinates. Each term is then a superposition of
products of gaussian functions of the individual Jacobi coordinates with
different widths, projected to angular momenta or 1. To avoid excessively
large dimensions and ``overcompleteness", stochastic methods were tested for
selecting the gaussians spanning the basis. For He, we were able to
calculate ground-state energies that are virtully exact within the subspace
defined by the arrangements and values, and we found that preselected
random sets of bases (with or without simulated annealing) yield excellent
numerical convergence to this ``exact" value with thoroughly truncated bases.
For He good energy convergence was achieved in a state space comprising
three arrangements with all , and there are indications showing that the
contributions of other subspaces are likely to be small. The He and He
energies are reproduced by the same effective force very well, and the matter
radii obtained are similar to those of other sophisticated calculations.Comment: Latex , 8 figures available on request, ATOMKI-4-1993-
Exotic nuclei far from the stability line
The recent availability of radioactive beams has opened up a new era in
nuclear physics. The interactions and structure of exotic nuclei close to the
drip lines have been studied extensively world wide, and it has been revealed
that unstable nuclei, having weakly bound nucleons, exhibit characteristic
features such as a halo structure and a soft dipole excitation. We here review
the developments of the physics of unstable nuclei in the past few decades. The
topics discussed in this Chapter include the halo and skin structures, the
Coulomb breakup, the dineutron correlation, the pair transfer reactions, the
two-nucleon radioactivity, the appearance of new magic numbers, and the pygmy
dipole resonances.Comment: 43 pages, 30 eps figures. chapter in "100 years of subatomic
physics", edited by E.M. Henley and S. Elli
The proton and neutron distribution in Na isotopes: the development of halo and shell structure
The interaction cross sections for reaction are calculated
using Glauber model. The continuum Hartree-Bogoliubov theory has been
generalized to treat the odd particle system and take the continuum into
account. The theory reproduces the experimental result quite well. The matter
distributions from the proton drip line to the neutron drip line in Na isotopes
have been systematically studied and presented. The relation between the shell
effects and the halos has been examined. The tail of the matter distribution
shows a strong dependence on the shell structure. The neutron N=28 closure
shell fails to appear due to the coming down of the and .
The development of the halo was understood as changes in the occupation in the
next shell or the sub-shell close to the continuum limit. The central proton
density is found to be decreasing near the neutron drip line, which is due to
the proton-neutron interaction. However the diffuseness of the proton density
does not change for the whole Na isotopes.Comment: 10 pages, 4 figure
Conceptual Design Report for the Scientific Program of the Super-FRS Experiment Collaboration
This Conceptual Design Report (CDR) presents the plans of the Super-FRS Experiment Collaboration for a variety of experiments, which build on the versatile high-resolution separator and spectrometer performance of the Super-FRS. The characteristic feature of these experiments is the fact that they use the separator as an integral part of the measurement. These experiments build on the experience of the collaboration and their scientific program pursued at the FRS in the last 25 years, but also includes recently developed novel topics.Under these premises, the Super-FRS Experiment Collaboration has identified ten major topics of current interest and with far-reaching scientific potential. In this CDR, the scientific case is briefly recapitulated and the conceptual design of the experiments, the setups and their implementation are described. Much of the needed equipment is already available or, if not, will be realized with new, additional resources and efforts outside the FAIR Cost Books. The related R&D works and some pilot experiments can be carried out at the existing FRS of GSI in FAIR Phase-0. On the midterm, the science program of this collaboration can start at the commissioning phase of the Super-FRS and will continue on the long term with the established full performance. Accordingly, the prototype equipment and other already existing devices can be tested and used at the FRS and can later, when completed or upgraded, be moved to the Super-FRS, see Appendix I. The related developments and organization of the Super-FRS Experiment Collaboration are described in Appendices II and III, respectively; the collaboration partners and institutes are listed in Appendix IV. The Super-FRS Experiment Collaboration is formally and firmly established and is a comprising part of the NUSTAR Collaboration. A large variety of modern nuclear physics experiments with new scientific possibilities and outstanding scientific potential were presented in the scientific program (GSI-Report 2014-4), which was very positively evaluated and approved by the FAIR-ECE in its 4th meeting in June 2014. In its report, the ECE encouraged the collaboration to develop TDRs. The present CDR is the next step on the way to TDRs for the ancillary equipment, that shall be integrated in the Super-FRS
Coulomb versus nuclear break-up of 11Be halo nucleus in a non perturbative framework
The 11Be break-up is calculated using a non perturbative time-dependent
quantum calculation. The evolution of the neutron halo wave function shows an
emission of neutron at large angles for grazing impact parameters and at
forward angles for large impact parameters. The neutron angular distribution is
deduced for the different targets and compared to experimental data. We
emphasize the diversity of diffraction mechanisms, in particular we discuss the
interplay of the nuclear effects such as the towing mode and the Coulomb
break-up. A good agreement is found with experimental data.Comment: 9 figures, this paper was accepter in Nuclear Physics A on sept, 200
IKEDA, the partner for exploring the nuclear highland far from the valley of stability
I have been collaborating with Ikeda since 1980’s when I started the experiment with radioactive nuclear beams. He has been interested in explaining the halo structure and binding energy of 11Li from the very beginning. From these studies, new basic concepts have been introduced, one of such important ideas is the soft resonance and cluster structure of halo nuclei. He also introduced the importance of the tensor forces on the halo formation, in particular for the correlation of two halo neutrons though s- and p- wave mixing. As an experimentalist, I have been trying to provide data to help him to develop these ideas. Here, I present the recent progresses in experimental studies. One is the first measurement of the two-neutron transfer reaction of 11Li to study the correlation between two halo neutrons. The other is a new on going experiment to obtain the direct evidence of the tensor forces in nuclei
Signatures of synchrotron emission and of electron acceleration in the X-ray spectra of Mrk 421
BL Lac objects undergo strong flux variations involving considerable changes
in their spectral shapes. We specifically investigate the X-ray spectral
evolution of Mrk 421 over a time span of about nine years. We aim at
statistically describing and physically understanding the large spectral
changes in X rays observed in Mrk 421 over this time span. We perform a
homogeneous spectral analysis of a wide data set including archived
observations with ASCA, BeppoSax, RXTE, as well as published and unpublished
XMM-Newton data. The presence of uncertainties is taken into account in our
correlation analysis. The significance of the correlations found and possible
spurious effects are studied with Monte Carlo simulations. We find that the
Mrk421 spectral energy distribution (SED) has a lower peak at energies that
vary in the range, 0.1-10 keV while its X-ray spectrum is definitely curved.
Parameterizing the X-ray spectra with a log-parabolic model, we find a positive
correlation between the position and the height of the SED peak. In addition,
we find a negative trend of the spectral curvature parameter vs. the SED peak
energy. We show that these relations between the spectral parameters are
consistent with statistical or stochastic acceleration of the emitting
particles, and provide insight into the physical processes occurring in BL Lac
nuclei.Comment: 11 pages, 5 fiures, Accepted for publication in A&
Structure Functions of Unstable Lithium Isotopes
We study both the spin-average and spin-dependent structure functions of the
lithium isotopes, Li, which could be measured at RIKEN and other
nuclear facilities in the future. It is found that the light-cone momentum
distribution of the valence neutron in the halo of Li is very sharp and
symmetric around y = 1, because of the weak binding. The EMC ratios for Li
isotopes are then calculated. We study the possibility of extracting the
neutron structure function from data for the nuclear structure functions of the
Li isotopes. Next we calculate the spin-dependent structure functions of
Li isotopes, which have spin of 3/2. The effect of the nuclear
binding and Fermi motion on the multipole spin structure function,
, is about 10% in the region x < 0.7, but it becomes quite
important at large x. The spin structure function of is also
investigated. Finally, we discuss the modification of the Gottfried and Bjorken
integrals in a nuclear medium and point out several candidates for a pair of
mirror nuclei to study the flavor-nonsinglet quark distributions in nuclei.Comment: 23 pages + 7 tables + 15 figure
Toward precision mass measurements of neutron-rich nuclei relevant to -process nucleosynthesis
The open question of where, when, and how the heavy elements beyond iron
enrich our Universe has triggered a new era in nuclear physics studies.\ Of all
the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is
a key quantity for revealing the origin of heavy elements beyond iron.\
Although the precise determination of this property is a great challenge,
enormous progress has been made in recent decades, and it has contributed
significantly to both nuclear structure and astrophysical nucleosynthesis
studies.\ In this review, we first survey our present knowledge of the nuclear
mass surface, emphasizing the importance of nuclear mass precision in
-process calculations.\ We then discuss recent progress in various methods
of nuclear mass measurement with a few selected examples.\ For each method, we
focus on recent breakthroughs and discuss possible ways of improving the
weighing of -process nuclides.Comment: 10 figures, review articles in Frontiers of Physic
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