1,123 research outputs found
Potential energy surfaces of actinide and transfermium nuclei from multi-dimensional constraint covariant density functional theories
Multi-dimensional constrained covariant density functional theories were
developed recently. In these theories, all shape degrees of freedom
\beta_{\lambda\mu} deformations with even \mu are allowed, e.g., \beta_{20},
\beta_{22}, \beta_{30}, \beta_{32}, \beta_{40}, \beta_{42}, \beta_{44}, and so
on and the CDFT functional can be one of the following four forms: the meson
exchange or point-coupling nucleon interactions combined with the non-linear or
density-dependent couplings. In this contribution, some applications of these
theories are presented. The potential energy surfaces of actinide nuclei in the
(\beta_{20}, \beta_{22}, \beta_{30}) deformation space are investigated. It is
found that besides the octupole deformation, the triaxiality also plays an
important role upon the second fission barriers. The non-axial
reflection-asymmetric \beta_{32} shape in some transfermium nuclei with N =
150, namely 246Cm, 248Cf, 250Fm, and 252No are studied.Comment: 7 pages, 6 figures; invited talk at the International Conference on
Nuclear Structure and Related Topics, Jul 02-July 7, 2012, Dubn
Multidimensionally-constrained relativistic mean-field study of triple-humped barriers in actinides
Potential energy surfaces (PES's) of actinide nuclei are characterized by a
two-humped barrier structure. At large deformations beyond the second barrier
the occurrence of a third one was predicted by Mic-Mac model calculations in
the 1970s, but contradictory results were later reported. In this paper,
triple-humped barriers in actinide nuclei are investigated with covariant
density functional theory (CDFT). Calculations are performed using the
multidimensionally-constrained relativistic mean field (MDC-RMF) model, with
functionals PC-PK1 and DD-ME2. Pairing correlations are treated in the BCS
approximation with a separable pairing force of finite range. Two-dimensional
PES's of Th and U are mapped and the
third minima on these surfaces are located. Then one-dimensional potential
energy curves along the fission path are analyzed in detail and the energies of
the second barrier, the third minimum, and the third barrier are determined.
DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and
U. The third minima in Th are very shallow, whereas those
in Th and U are quite prominent. With PC-PK1 a third
barrier is found only in Th. Single-nucleon levels around the
Fermi surface are analyzed in Th, and it is found that the formation of
the third minimum is mainly due to the proton energy gap at and . The possible occurrence of a third
barrier in actinide nuclei depends on the effective interaction used in
multidimensional CDFT calculations. More pronounced minima are predicted by the
DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third
well in Th isotopes decreases with increasing neutron number. The origin of the
third minimum is due to the proton shell gap at relevant deformations.Comment: 10 pages, 7 figures; Phys. Rev. C, in press; due to the limitation
"The abstract field cannot be longer than 1,920 characters", the abstract
appearing here is slightly shorter than that in the PDF fil
The , decays in the perturbative QCD approach
Nonleptonic two body decays including radially excited or
mesons in the final state are studied using the perturbative QCD
approach based on factorization. The charmonium distribution amplitudes
are extracted from the Schrdinger states for the
harmonic oscillator potential. Utilizing these distribution amplitudes, we
calculate the numerical results of the
transition form factors and branching fractions of decays. The ratio between two decay modes and is compatible with the experimental
data within uncertainties, which indicate that the harmonic oscillator wave
functions for and work well. It is found that the
branching fraction of , which is dominated by the
twist-3 charmonium distribution amplitude, can reach the order of . We
hope it can be measured soon in the LHCb experiment.Comment: 9 pages, 3 figures,3 Table
Rectal hemangiopericytoma in a 37-year-old woman: a case report and review of the literature
<p>Abstract</p> <p>Introduction</p> <p>Hemangiopericytoma is an uncommon perivascular tumor. Rectal Hemangiopericytomas are extremely rare. To the best of our knowledge, only two cases have been reported in the literature.</p> <p>Case presentation</p> <p>We report the case of a 37-year-old Asian woman with an Hemangiopericytoma rising from the anterior wall of her rectum. Abdominopelvic computed tomography showed a 7.4 cm solid mass between her uterus and her rectum. Heterogeneous gradual enhancement after intravenous injection of contrast material was noted with several tortuous vessels around her tumor. Intra-operative findings indicated a capsule and well-circumscribed solid tumor connecting with the anterior wall of her rectum by a small pedicle. With immunohistochemical stains, her tumor cells reacted positive for Bcl-2, CD34, and ki67 and negative for CD10, CD117, S100, and Desmin. Follow-up computed tomography scans have shown no tumor recurrence or metastasis signs.</p> <p>Conclusions</p> <p>Rectal Hemangiopericytoma is a rare tumor with non-specific imaging findings. Hemangiopericytomas should be included in the differential list when a massive tumor with heterogeneously gradual enhancement in the regions of the rectum is encountered.</p
- …