139 research outputs found
Three-body model for an isoscalar spin-triplet neutron-proton pair in
We discuss the isoscalar pairing correlation in the low-lying
states of nucleus. To this end, we employ
three-body model with the model space constructed by
self-consistent mean-field calculations. The model is developed with both
non-relativistic and relativistic effective interactions, the latter of which
are found to be more realistic for the present case due to the pseudo-spin
symmetry. It turns out that the pairing scheme is strongly
hindered in Sb with the relativistic model because of the near
degeneracy of the and orbitals in the valence space. This
pair-breaking effect is clearly seen in the charge-exchange Gamow-Teller-type
transitions rather than in the binding energies of and states.Comment: 12 pages, 10 figures. The title has been changed. Accepted for
publication in Phys. Rev.
Highlights from the Telescope Array Experiments
The Telescope Array (TA) is the largest hybrid cosmic ray detector in the
Northern Hemisphere, which observes primary particles in the energy range from
2 PeV to 100 EeV. The main TA detector consists of 507 plastic scintillation
counters on a 1.2-km spacing square grid and fluorescence detectors at three
stations overlooking the sky above the surface detector array. The TA Low
energy Extension (TALE) hybrid detectors, which consists of ten fluorescence
telescopes, and 80 infill surface detectors with 400-m and 600-m spacing, has
continued to provide stable observations since its construction completion in
2018. The TAx4, a plan to quadruple the detection area of TA is also ongoing.
About half of the planned detectors have been deployed, and the current TAx4
continues to operate stably as a hybrid detector. I review the present status
of the TA experiment and the recent results on the cosmic-ray anisotropy, mass
composition and energy spectrum.Comment: Submission to SciPost Phys. Pro
Exotic Structure of Carbon Isotopes
We studied firstly the ground state properties of C-isotopes using a deformed
Hartree-Fock (HF)+ BCS model with Skyrme interactions. Shallow deformation
minima are found in several neutronrich C-isotopes. It is shown also that
the deformation minima appear in both the oblate and the prolate sides in
C and C having almost the same binding energies. Secondly, we
carried out shell model calculations to study electromagnetic moments and
electric dipole transitions of the C-isotopes. We point out the clear
configuration dependence of the quadrupole and magnetic moments in the odd
C-isotopes, which will be useful to find out the deformations and the
spin-parities of the ground states of these nuclei. We studied electric dipole
states of C-isotopes focusing on the interplay between low energy Pigmy
strength and giant dipole resonances.
Reasonable agreement is obtained with available experimental data for the
photoreaction cross sections both in the low energy region below =14 MeV and in the high energy giant resonance region (14 MeV 30 MeV).
The calculated transition strength below dipole giant resonance (14 MeV) in heavier C-isotopes than C is found to exhaust
about of the classical Thomas-Reiche-Kuhn sum rule value and
of the cluster sum rule value.Comment: 31 pages, 19 eps figure
Collisions of Deformed Nuclei and Superheavy-Element Production
A detailed understanding of complete fusion cross sections in heavy-ion
collisions requires a consideration of the effects of the deformation of the
projectile and target. Our aim here is to show that deformation and orientation
of the colliding nuclei have a very significant effect on the fusion-barrier
height and on the compactness of the touching configuration. To facilitate
discussions of fusion configurations of deformed nuclei, we develop a
classification scheme and introduce a notation convention for these
configurations. We discuss particular deformations and orientations that lead
to compact touching configurations and to fusion-barrier heights that
correspond to fairly low excitation energies of the compound systems. Such
configurations should be the most favorable for producing superheavy elements.
We analyse a few projectile-target combinations whose deformations allow
favorable entrance-channel configurations and whose proton and neutron numbers
lead to compound systems in a part of the superheavy region where alpha
half-lives are calculated to be observable, that is, longer than 1 microsecond.Comment: 15 pages. LaTeX with iopconf.sty style file. Presented at 2nd
RIKEN/INFN Joint Symposium, Wako-shi, Saitama, Japan, May 22-26, 1995. To be
published in symposium proceedings by World Scientific, Singapore. Seven
figures not included here. PostScript version with figures available at
http://t2.lanl.gov/pub/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/riken9
Shell Structure and -Tensor Correlations in Density-Dependent Relativistic Hartree-Fock theory
A new effective interaction PKA1 with -tensor couplings for the
density-dependent relativistic Hartree-Fock (DDRHF) theory is presented. It is
obtained by fitting selected empirical ground state and shell structure
properties. It provides satisfactory descriptions of nuclear matter and the
ground state properties of finite nuclei at the same quantitative level as
recent DDRHF and RMF models. Significant improvement on the single-particle
spectra is also found due to the inclusion of -tensor couplings. As a
result, PKA1 cures a common disease of the existing DDRHF and RMF Lagrangians,
namely the artificial shells at 58 and 92, and recovers the realistic sub-shell
closure at 64. Moreover, the proper spin-orbit splittings and well-conserved
pseudo-spin symmetry are obtained with the new effective interaction PKA1. Due
to the extra binding introduced by the -tensor correlations, the balance
between the nuclear attractions and the repulsions is changed and this
constitutes the physical reason for the improvement of the nuclear shell
structure.Comment: 20 pages, 11 figures, 6 table
Superdeformed hypernuclei with antisymmetrized molecular dynamics
The response to the addition of a hyperon is investigated for the
deformed states such as superdeformation in Ca, Sc and Sc. In the present study, we use the antisymmetrized
molecular dynamics (AMD) model. It is pointed out that many kinds of deformed
bands appear in Sc and Sc. Especially, it is found that there
exists superdeformed states in Sc. By the addition of a
particle to Ca, Sc and Sc, it is predicted, for the first
time, that the superdeformed states exist in the hypernuclei Ca
and Sc. The manifestation of the dependence of the
-separation energy on nuclear deformation such as spherical, normal
deformation and superdeformation is shown in the energy spectra of
Ca, Sc and Sc hypernuclei.Comment: 24 pages, 8 figure
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