Nuclear Theory·nucl-th

Tuesday·March 15, 2016

12 papers—8 primary·4 cross-listed

01
Determination of a dineutron correlation in Borromean nuclei via a quasi-free knockout ( $p, p n$ ) reaction?
Yuma Kikuchi · Kazuyuki Ogata · Yuki Kubota · Masaki Sasano · Tomohiro Uesaka
To discuss the dineutron correlation in the ground state, the quasi-free neutron knockout reaction on $^{6}$ He is investigated.In the present work, the momentum distribution of the two emitted neutrons is calculated with the $α$ ~+~ $n$ ~+~ $n$ three-body model and a simple reaction model to assess the effects of the knockout process via the $^{5}$ He resonance and the target dependence in the momentum distribution. A clear signature of the dineutron correlation can be obtained by choosing the kinematical condition so the process via the $^{5}$ He resonance is excluded because the $^{5}$ He resonance drastically changes the momentum distribution. Using the proton target is important in the quantitative discussion on the dineutron correlation by the knockout reaction. In addition to theoretical arguments, a possible experimental setup to determine the dineutron correlation via the quasi-free knockout reaction is considered.
nucl-thnucl-exPTEP(2016)·19 citations
02
Photodisintegration cross section of $^{9}$ Be up to 16 MeV in the $α$ + $α$ + n three-body model
Yuma Kikuchi · Myagmarjav Odsuren · Takayuki Myo · Kiyoshi Katō
The photodisintegration of $^{9}$ Be in the energy region lower than $E_{γ} = 16$ MeV is investigated by using the $α$ ~+~ $α$ ~+~ $n$ three-body model and the complex scaling method. The cross section exhibits two aspects in the different two energy regions. In the low energy region up to $E_{γ} = 6$ MeV, the cross section is explained by the transition strengths into the excited resonant states of $^{9}$ Be, while the dipole transition into the non-resonant continuum states of $^{8}$ Be(2 $^{+}$ )~+~ $n$ dominates the cross section in the energy region of $6 \leq E_{γ} \leq 16$ MeV. Furthermore, it is shown that the dipole strength at $E_{γ} \sim 8$ MeV is understood to be caused by the single-neutron excitation from the $^{8}$ Be(2 $^{+}$ )~ $\otimes$ ~ $ν p_{3/2}$ configuration in the ground state.
nucl-thPRC(2016)·15 citations
03
Nuclear $β^{-}$ -decay half-lives for $f p$ and $f p g$ shell nuclei
Vikas Kumar · P.C. Srivastava · Hantao Li
In the present work we calculate the allowed $β^{-}$ -decay half-lives of nuclei with $Z = 20 - 30$ and N $\leq$ 50 systematically under the framework of the nuclear shell model. A recent study shows that some nuclei in this region belong to the island of inversion. We perform calculation for $f p$ shell nuclei using KB3G effective interaction. In the case of Ni, Cu, and Zn, we used JUN45 effective interaction. Theoretical results of $Q$ values, half-lives, excitation energies, log $f t$ values, and branching fractions are discussed and compared with the experimental data. In the Ni region, we also compared our calculated results with recent experimental data [Z. Y. Xu {\it et al.}, \emph{Phys. Rev. Lett.} \textbf{113}, 032505, 2014]. Present results agree with the experimental data of half-lives in comparison to QRPA.
nucl-thJ.Phys.G(2016)·43 citations
04
Pionic contribution in the Drell-Yan dilepton production cross section in p-Cu collision in the framework of the shell and Fermi gas models
R. Rostami🇮🇷 · F. Zolfagharpour🇮🇷
To investigate the high mass dilepton production cross section produced due to the Drell-Yan process in hadronic collisions such as nucleon- nucleus, the valence and sea quarks distribution functions inside nucleus is used. In this study, in the framework of the shell and Fermi gas models, by adding quarks distribution functions of pions inside nucleus besides the quarks distribution functions of bound nucleons, the changes in the dilepton production cross section were investigated. For this reason, pionic contribution in the structure function of 63Cunucleus and its EMC ratio was first studied using the aforementioned models. Then, in the framework of the Drell-Yan process using GRV's nucleons and pions quarks distribution functions, the high mass dilepton production cross section in p-cu collision was calculated and compared with the available experimental data. The extracted results, based on the two mentioned models, were greatly the same and by considering the pionic contribution, the theoretical results were consistent with the experimental data.
nucl-thhep-ph0 citations
05
Role of scalar dibaryon and $f_{0} (500)$ in the isovector channel of low-energy neutron-proton scattering
Werner Deinet🇩🇪 · Khaled Teilab🇩🇪 · Francesco Giacosa🇵🇱 · Dirk H. Rischke🇩🇪
We calculate the total and the differential cross section for $n p$ scattering at low energies in the isospin $I = 1$ channel within the so-called extended Linear Sigma Model. This model contains conventional (pseudo)scalar and (axial--)vector mesons, as well as the nucleon and its chiral partner within the mirror assignment. In order to obtain good agreement with experimental data analysis results we need to consider two additional resonances: the lightest scalar state $f_{0} (500)$ and a dibaryon state with quantum numbers $I = 1,$ $J^{P} = 0^{+}$ (also known as $^{1} S_{0}$ resonance). The resonance $f_{0} (500)$ is coupled to nucleons in a chirally invariant way through the mirror assignment and is crucial for a qualitatively correct description of the shape of the differential cross section. On the other hand, the dibaryon is exchanged in the $s$ --channel and is responsible of the large cross section close to threshold. We compare our results to data analysis results performed by the SAID program of the CNS Data Analysis Center (in the following "SAID results").
nucl-thhep-phPRC(2016)·4 citations
06
Nuclear shell structures in terms of classical periodic orbits
Ken-ichiro Arita
Semiclassical periodic-orbit theory (POT) is applied to the physics of nuclear structures, with the use of a realistic nuclear mean-field model given by the radial power-law potential. Evolution of deformed shell structures, which are responsible for various nuclear deformations, are clearly understood from the contribution of short classical periodic orbits (POs). Bifurcations of short POs, which imply underlying local dynamical symmetry, play significant role there. The effect of the spin degree of freedom is also investigated in relevance to the pseudospin symmetry in spherical nuclei and the prolate-oblate asymmetry in shell structures of nuclei with quadrupole-type deformations.
nucl-thPhys.Scripta(2016)·10 citations
07
High-spin structure of $^{87}$ Sr and $^{87}$ Zr nuclei : shell model interpretation
P. C. Srivastava · Vikas Kumar · M. J. Ermamatov
In the present work we report a comprehensive analysis of shell model results for high-spin states of $^{87}$ Sr and $^{87}$ Zr for recently available experimental data within the full $f_{5/2} p g_{9/2}$ model space using JUN45 and jj44b effective interactions developed for this model space. In this work we have compared the energy levels, electromagnetic transition probabilities, quadrupole and magnetic moments with available experimental data. We have confirmed structure of high-spin states of these two nuclei which were tentatively assigned in the recent experimental work. In the case of $^{87}$ Sr, for positive parity states up to $\sim$ 7.5 MeV, both interactions predict very good agreement with experimental data, while negative parity states are slightly suppressed in jj44b calculation.For the $^{87}$ Zr nucleus, the jj44b interaction predicts higher energies for the negative parity states beyond $J \geq 27/ 2^{-}$ . The configuration, which have one hole in $ν g_{9/2}$ orbital, is responsible for generating the states in $^{87}$ Sr. In the case of $^{87}$ Zr, low-lying positive parity states come with the configuration having three holes in the $ν g_{9/2}$ , while the odd-parity states have configuration $ν (f_{5/2}^{- 1} g_{9/2}^{- 2})$ .
nucl-thActa Phys.Polon.B(2016)·3 citations
08
Theoretical description of nuclear collective excitations
Anton Repko
Density functional theory is a preferred microscopic method for calculation of nuclear properties over the whole nuclear chart. Besides ground-state properties, which are calculated by Hartree-Fock theory, nuclear excitations can be described by means of Random Phase Approximation (RPA). The main objective of the present work is to give Skyrme RPA formalism for spherically symmetric nuclei, using the techniques of angular-momentum coupling. Various auxiliary topics, such as Hartree-Fock theory, Coulomb integral, center-of-mass corrections and pairing, are treated as well. RPA method is derived also for axially deformed nuclei. The derived formulae are then implemented in the computer code and utilized for calculation of some physical results. After thorough investigation of the precision aspects of the calculation, the following topics are treated as examples: toroidal nature of the low-energy (pygmy) part of the E1 resonance, giant resonances of various multipolarities in deformed nucleus Sm-154, and magnetic dipole (M1) transitions in deformed Cr-50. Keywords: Random Phase Approximation, Skyrme functional, giant resonances in nuclei, reduced matrix elements I thank Jiri Mares and F. Knapp for their comments, which were taken into account in the first revision.
nucl-th5 citations

Affiliations

first authorsco-authorsvia INSPIRE