Nuclear Theory·nucl-th

Tuesday·April 21, 2015

14 papers—9 primary·5 cross-listed

01
[Submitted on 18 Apr 2015]
Central depressions in the charge density profiles of the nuclei around $^{46}$ Ar
Jun Ling Song · Qiang Zhao · Wen Hui Long
The occurrence of the proton bubble-like structure has been studied within the relativistic Hartree-Fock-Bogoliubov (RHFB) and relativistic Hartree-Bogoliubov (RHB) theories by exploring the bulk properties, the charge density profiles and single proton spectra of argon isotopes and $N = 28$ isotones. It is found that the RHFB calculations with PKA1 effective interaction, which can properly reproduce the charge radii of argon isotopes and the $Z = 16$ proton shell nearby, do not support the occurrence of the proton bubble-like structure in argon isotopes due to the prediction of deeper bound proton orbit $π 2 s_{1/2}$ than $π 1 d_{3/2}$ . For $N = 28$ isotones, $^{42}$ Si and $^{40}$ Mg are predicted by both RHFB and RHB models to have the proton bubble-like structure, owing to the large gap between the proton $π 2 s_{1/2}$ and $π 1 d_{5/2}$ orbits, namely the $Z = 14$ proton shell. Therefore, $^{42}$ Si is proposed as the potential candidate of proton bubble nucleus, which has longer life-time than $^{40}$ Mg.
Comments:
5 figures, 2 tables, and 9 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.04738 [pdf]
1 citation
02
[Submitted on 19 Apr 2015]
Octupole deformation in light actinides within an analytic quadrupole octupole axially symmetric model with Davidson potential
Dennis Bonatsos · Andriana Martinou · N. Minkov · S. Karampagia · D. Petrellis
The analytic quadrupole octupole axially symmetric model, which had successfully predicted 226Ra and 226Th as lying at the border between the regions of octupole deformation and octupole vibrations in the light actinides using an infinite well potential (AQOA-IW), is made applicable to a wider region of nuclei exhibiting octupole deformation, through the use of a Davidson potential (AQOA-D). Analytic expressions for energy spectra and B(E1), B(E2), B(E3) transition rates are derived. The spectra of 222-226Ra and 224,226Th are described in terms of the two parameters phi_0 (expressing the relative amount of octupole vs. quadrupole deformation) and beta_0 (the position of the minimum of the Davidson potential), while the recently determined B(EL) transition rates of 224Ra, presenting stable octupole deformation, are successfully reproduced. A procedure for gradually determining the parameters appearing in the B(EL) transitions from a minimum set of data, thus increasing the predictive power of the model, is outlined.
Comments:
20 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.04837 [pdf]
PRC(2015)·29 citations
03
[Submitted on 19 Apr 2015]
Thermonuclear Processes for Three Body System in the Potential Cluster Model
S.B. Dubovichenko · A.V. Dzhazairov-Kakhramanov
The manuscript is devoted to the description of the results obtained in the frame of the modified potential cluster model with the classification of states according to Young tableaux for neutron and proton radiative capture processes on 2H at thermal and astrophysical energies. It demonstrates methods of application that were obtained on the basis of phase shift analysis and characteristics of the bound states of 2H potentials for consideration of the radiative capture processes. First reaction of the proton capture directly takes part in the pp solar cycle, where it is the second reaction. The neutron capture is not a part of usual thermonuclear cycles in the Sun and stars, but can take part in the processes of primordial nucleosynthesis, following at formation and evolution of our entire Universe.
Comments:
arXiv admin note: text overlap with arXiv:1202.1995
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.04899 [pdf]
NPA(2015)·26 citations
04
[Submitted on 20 Apr 2015]
Microscopic study of low-lying spectra of $Λ$ hypernuclei based on a beyond-mean-field approach with covariant energy density functional
H. Mei🇯🇵 · K. Hagino🇯🇵 · J.M. Yao🇯🇵 · T. Motoba🇯🇵
We present a detailed formalism of the microscopic particle-rotor model for hypernuclear low-lying states based on a covariant density functional theory. In this method, the hypernuclear states are constructed by coupling a hyperon to low-lying states of the core nucleus, which are described by the generator coordinate method (GCM) with the particle number and angular momentum projections. We apply this method to study in detail the low-lying spectrum of $_{Λ}^{13}$ C and $_{Λ}^{21}$ Ne hypernuclei. We also briefly discuss the structure of $_{Λ}^{155}$ Sm as an example of heavy deformed hypernuclei. It is shown that the low-lying excitation spectrum with positive parity states of the hypernuclei, which are dominated by $Λ$ hyperon in $s$ -orbital coupled to the core states, are similar to that for the corresponding core states, while the electric quadrupole transition strength, $B (E 2)$ , from the 2 $_{1}^{+}$ state to the ground state is reduced according to the mass number of the hypernuclei. Our study indicates that the energy splitting between the first 1/2 $^{-}$ and 3/2 $^{-}$ hypernuclear states is generally small for all the hypernuclei which we study. However, their configurations depend much on the properties of a core nucleus, in particular on the sign of deformation parameter. That is, the first $1/ 2^{-}$ and $3/ 2^{-}$ states in $_{Λ}^{13}$ C are dominated by a single configuration with $Λ$ particle in the $p$ -wave orbits and thus providing good candidates for a study of the $Λ$ spin-orbit splitting. On the other hand, those states in the other hypernuclei exhibit a large configuration mixing and thus their energy difference cannot be interpreted as the spin-orbit splitting for the $p$ -orbits.
Comments:
18 pages, 20 eps figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1504.04924 [pdf]
PRC(2015)·35 citations
05
[Submitted on 20 Apr 2015]
Ground-state energies and charge radii of $^{4}$ He, $^{16}$ O, $^{40}$ Ca, and $^{56}$ Ni in the unitary-model-operator approach
Takayuki Miyagi · Takashi Abe · Ryoji Okamoto · Takaharu Otsuka
We study the nuclear ground-state properties by using the unitary-model-operator approach (UMOA). Recently, the particle-basis formalism has been introduced in the UMOA and enables us to employ the charge-dependent nucleon-nucleon interaction. We evaluate the ground-state energies and charge radii of $^{4}$ He, $^{16}$ O, $^{40}$ Ca, and $^{56}$ Ni with the charge-dependent Bonn potential. The ground-state energy is dominated by the contributions from the one- and two-body cluster terms, while, for the radius, the one-particle-one-hole excitations are more important than the two-particle-two-hole excitations. The calculated results reproduce the trend of experimental data of the saturation property for finite nuclei.
Comments:
8 pages, 1 figure, published in Prog. Theor. Exp. Phys
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.04965 [pdf]
PTEP(2015)·3 citations
06
[Submitted on 20 Apr 2015]
Shape phase transition in the odd Sm nuclei: effective order parameter and odd-even effect
Yu Zhang · Xin Guan · Yin Wang · Yan Zuo · Li-na Bao · Feng Pan
Some binding-energy-related quantities serving as effective order parameters have been used to analyze the shape phase transition in the odd Sm nuclei. It is found that the signals of phase transition in the odd Sm nuclei are greatly enhanced in contrast to the even Sm nuclei. A further analysis shows that the transitional behaviors related to pairing in the Sm nuclei can be well described by the mean field plus pairing interaction model, with a monotonic decrease in the pairing strength $G$ .
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.05026 [pdf]
CPC(2015)·4 citations
07
[Submitted on 20 Apr 2015]
Triaxial dynamics in the quadrupole-deformed rotor
Qiu-Yue Li · Xiao-Xiang Wang · Yan Zuo · Yu Zhang · Feng Pan
The triaxial dynamics of the quadrupole-deformed rotor model of both the rigid and the irrotational type have been investigated in detail. The results indicate that level patterns and E2 transitional characters of the two types of the model can be matched with each other to the leading order of the deformation parameter $β$ . Especially, it is found that the dynamical structure of the irrotational type with most triaxial deformation ( $γ = 3 0^{\circ}$ ) is equivalent to that of the rigid type with oblate deformation ( $γ = 6 0^{\circ}$ ), and the associated spectrum can be classified into the standard rotational bands obeying the rotational $L (L + 1)$ -law or regrouped into a new ground- and $γ$ -band with odd-even staggering in the new $γ$ -band commonly recognized as a signature of the triaxiality. The differences between the two types of the model in this case are emphasized especially on the E2 transitional characters.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.05034 [pdf]
CPC(2016)·6 citations
08
[Submitted on 20 Apr 2015]
Electromagnetic Structure of Few-Nucleon Ground States
L.E. Marcucci🇮🇹 · F. Gross🇺🇸 · M.T. Pena🇵🇹 · M. Piarulli🇺🇸 · R. Schiavilla🇺🇸 · I. Sick🇨🇭 · A. Stadler · J.W. Van Orden🇺🇸 · M. Viviani🇮🇹
Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled $χ$ EFT); the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled CST). For momentum transfers below $Q ≲ 5$ fm $^{- 1}$ there is satisfactory agreement between experimental data and theoretical results in all three approaches. However, at $Q ≳ 5$ fm $^{- 1}$ , particularly in the case of the deuteron, a relativistic treatment of the dynamics, as is done in the CST, is necessary. The experimental data on the deuteron $A$ structure function extend to $Q ≃ 12$ fm $^{- 1}$ , and the close agreement between these data and the CST results suggests that, even in this extreme kinematical regime, there is no evidence for new effects coming from quark and gluon degrees of freedom at short distances.
Comments:
66 pages, 23 figures, topical review submitted to J. Phys. G: Nucl. Part. Phys
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1504.05063 [pdf]
J.Phys.G(2016)·67 citations
09
[Submitted on 20 Apr 2015]
Three-pion exchange nucleon-nucleon potentials with virtual $Δ$ -isobar excitation
N. Kaiser🇩🇪
The nucleon-nucleon interaction arising from the exchange of three pions and the excitation of $Δ (1232)$ -isobars in intermediate states is studied. Approximating the $Δ$ -propagator by the inverse $Δ$ N mass-splitting, analytical expressions are derived for the spectral-functions of the isoscalar and isovector central, spin-spin and tensor NN-potentials in momentum-space. A trans- lation of the spectral-functions into coordinate-space potentials reveals that the main effect of these specific exchange and excitation mechanisms is a repulsive isoscalar central NN-potential.
Comments:
12 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.05131 [pdf]
PRC(2015)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE