Nuclear Theory·nucl-th

Tuesday·March 15, 2016

12 papers—8 primary·4 cross-listed

01
[Submitted on 12 Mar 2016]
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.
Comments:
19 pages, 10 figures, 2 tables, to be published in PTEP
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1603.03858 [pdf]
PTEP(2016)·19 citations
02
[Submitted on 12 Mar 2016]
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.
Comments:
17 pages, 6 figures, 3 tables, submitted to PRC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.03861 [pdf]
PRC(2016)·15 citations
03
[Submitted on 12 Mar 2016]
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.
Comments:
Accepted in Journal of Physics G: Nuclear and Particle Physics
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.03897 [pdf]
J.Phys.G(2016)·43 citations
04
[Submitted on 13 Mar 2016]
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.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1603.04009 [pdf]
0 citations
05
[Submitted on 14 Mar 2016]
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").
Comments:
13 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1603.04312 [pdf]
PRC(2016)·4 citations
06
[Submitted on 14 Mar 2016]
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.
Comments:
Published version, 26 pages, 33 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.04316 [pdf]
Phys.Scripta(2016)·10 citations
07
[Submitted on 14 Mar 2016]
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 $ν (f_{5/2}^{- 1} g_{9/2}^{- 2})$ .
Comments:
14 pages,4 figures; Acta Physica Polonica B (in press)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.04354 [pdf]
Acta Phys.Polon.B(2016)·3 citations
08
[Submitted on 14 Mar 2016]
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.
Comments:
PhD thesis (Charles University in Prague), v4: corrected some misprints; updated spherical HF+RPA program: numerical optimizations, added spurious projection, (e,e') formfactors and effective current
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1603.04383 [pdf]
5 citations
09
[Submitted on 12 Mar 2016] (cross-list from hep-ph)
Thermo-magnetic effects in quark matter: Nambu--Jona-Lasinio model constrained by lattice QCD
R. L. S. Farias🇧🇷 · V. S. Timoteo🇧🇷 · S. S. Avancini🇧🇷 · M. B. Pinto🇧🇷 · G. Krein🇧🇷
The phenomenon of inverse magnetic catalysis of chiral symmetry in QCD predicted by lattice simulations can be reproduced within the Nambu--Jona-Lasinio model if the coupling~ $G$ of the model decreases with the strength $B$ of the magnetic field and temperature~ $T$ . The thermo-magnetic dependence of $G (B, T)$ is obtained by fitting recent lattice QCD predictions for the chiral transition order parameter. Different thermodynamic quantities of magnetized quark matter evaluated with $G (B, T)$ are compared with the ones obtained at constant coupling, $G$ . The model with $G (B, T)$ predicts a more dramatic chiral transition as the field intensity increases. In addition, the pressure and magnetization always increase with $B$ for a given temperature. Being parametrized by four magnetic field dependent coefficients and having a rather simple exponential thermal dependence our accurate ansatz for the coupling constant can be easily implemented to improve typical model applications to magnetized quark matter.
Comments:
13 pages, 9 figures, v3 EPJA version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1603.03847 [pdf]
EPJA(2017)·146 citations
10
[Submitted on 12 Mar 2016] (cross-list from hep-ph)
Evidence for Some New Hyperon Resonances -- to be Checked by $K_{L}$ Beam Experiments
B. S. Zou🇨🇳
Quenched and unquenched quark models predict very different patterns for the spectrum of the low excited hyperon states. Evidence is accumulating for the existence of some new hyperon resonances, such as a $Σ^{*}$ of spin-parity $J^{P} = 1/ 2^{-}$ around 1400 MeV instead of 1620 MeV as listed in PDG, a new $Σ (1540) 3/ 2^{-}$ resonance, a new narrow $Λ (1670) 3/ 2^{-}$ resonance and a new $Λ (1680) 3/ 2^{+}$ resonance. All these new hyperon resonances fit in the predicted pattern of the unquenched quark models very well. It is extremely important to check and establish the spectrum of these low excited hyperon states by the proposed $K_{L}$ beam experiments at JLAB.
Comments:
Talk for the workshop on Physics with Neutral Kaon beam at JLab
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.03927 [pdf]
4 citations
11
[Submitted on 14 Mar 2016] (cross-list from hep-ph)
Hadronic molecular states from the $K K ˉ^{*}$ interaction
Pei-Liang Lü🇨🇳 · Jun He🇨🇳
In this work, the $K K ˉ^{*}$ interaction is studied in a quasipotential Bethe-Salpeter equation approach combined with the one-boson-exchange model. With the help of the hidden-gauge Lagrangian, the exchanges of pseudoscalar mesons ( $π$ and $η$ ) and vector mesons ( $ρ$ , $ω$ and $ϕ$ ) are considered to describe the $K K ˉ^{*}$ interaction. Besides the direct vector-meson exchange which can be related to the Weinberg-Tomozawa term, pseudoscalar-meson exchanges also play important roles in the mechanism of the $K K ˉ^{*}$ interaction. The poles of scattering amplitude are searched to find the molecular states produced from the $K K ˉ^{*}$ interaction. In the case of quantum number $I^{G} (J^{P C}) = 0^{+} (1^{++})$ , a pole is found with a reasonable cutoff, which can be related to the $f_{1} (1285)$ in experiment. Another bound state with $0^{-} (1^{+-})$ is also produced from the $K K ˉ^{*}$ interaction, which can be related to the $h_{1} (1380)$ . In the isovector sector, the interaction is much weaker and a bound state with $1^{+} (1^{+})$ relevant to the $b_{1} (1235)$ is produced but at a larger cutoff. Our results suggest that in the hadronic molecular state picture the $f_{1} (1285)$ and $b_{1} (1235)$ are the strange partners of the $X (3872)$ and $Z_{c} (3900)$ , respectively.
Comments:
5 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.04168 [pdf]
EPJA(2016)·20 citations
12
[Submitted on 14 Mar 2016] (cross-list from hep-ph)
Evidence of strong proton shape fluctuations from incoherent diffraction
Heikki Mäntysaari🇺🇸 · Björn Schenke🇺🇸
We show within the saturation framework that measurements of exclusive vector meson production at high energy provide evidence for strong geometric fluctuations of the proton. In comparison, the effect of saturation scale and color charge fluctuations is weak. This knowledge will allow detailed future measurements of the incoherent cross section to tightly constrain the fluctuating geometry of the proton as a function of the parton momentum fraction $x$ .
Comments:
7 pages, 4 figures. v2: typos fixed and references added. To be published in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.04349 [pdf]
PRL(2016)·248 citations

Affiliations

first authorsco-authorsvia INSPIRE