Nuclear Theory·nucl-th

Thursday·September 13, 2018

7 papers—6 primary·1 cross-listed

01
Possible determination of high-lying single particle components with (p,d) reactions
Y.P. Xu · D.Y. Pang · X.Y. Yun · S. Kubono · C.A. Bertulani · C.X. Yuan
A detailed feasibility study on deducing the high-lying single-particle components (HLSPCs), which are important but used to be ignored, in the ground and low-lying excited states of even-even light nuclei is performed by analyses of $(p, d)$ reactions with \nuc{12}{C}, \nuc{24}{Mg}, \nuc{28}{Si}, and \nuc{40}{Ca} targets at 51.93 MeV. Coupled reaction channels (CRC) analyses have been made for $(p, d)$ transitions to the $j$ -forbidden excited states in \nuc{11}{C} ( $\frac{5}{2}^{-}$ , 4.32 MeV), \nuc{23}{Mg} ( $\frac{7}{2}^{+}$ , 2.05 MeV), \nuc{27}{Si} ( $\frac{7}{2}^{+}$ , 2.16 MeV) and \nuc{39}{Ca} ( $\frac{9}{2}^{-}$ , 3.64 MeV), including the major allowed transition components together with direct components of HLSPCs. Spectroscopic amplitudes of the HLSPCs are deduced by fitting the angular distributions of the ground and the $j$ -forbidden excited states simultaneously. The present analysis demonstrates for the first time that information about HLSPCs in atomic nuclei can be obtained from analysis of $(p, d)$ reactions.
nucl-thPRC(2018)·5 citations
02
The enhancement of $v_{4}$ in nuclear collisions at the highest densities signals a first order phase transition
Yasushi Nara🇯🇵 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪
The beam energy dependence of $v_{4}$ (the quadrupole moment of the transverse radial flow) is sensitive to the nuclear equation of state (EoS) in mid-central Au + Au collisions at the energy range of $3 < s_{N N} < 30$ GeV, which is investigated within the hadronic transport model JAM. Different equations of state, namely, a free hadron gas, a first-order phase transition and a crossover are compared. An enhancement of $v_{4}$ at $s_{N N} \approx 6$ GeV is predicted for an EoS with a first-order phase transition. This enhanced $v_{4}$ flow is driven by both the enhancement of $v_{2}$ as well as the positive contribution to $v_{4}$ from the squeeze-out of spectator particles which turn into participants due to the admixture of the strong collective flow in the shocked, compressed nuclear matter.
nucl-thhep-phnucl-exEPJA(2018)·18 citations
03
Symmetry Conserving Configuration Mixing description of odd mass nuclei
M. Borrajo · J. Luis Egido
We present a self-consistent theory for the description of the spectroscopic properties of odd nuclei which includes exact blocking, particle-number and angular-momentum projection and configuration mixing. In our theory the pairing correlations are treated in a variation-after-projection approach and the triaxial deformation parameters are explicitly considered as generator coordinates. The angular-momentum and particle-number symmetries are exactly recovered. The use of the effective finite-range density-dependent Gogny force in the calculations provides an added value to the theoretical results. We apply the theory to the textbook example of 25Mg and, although this nucleus has been thoroughly studied in the past, we still provide a novel view of nuclear phenomena taking place in this nucleus. We obtain an overall good agreement with the known experimental energies and transition probabilities without any additional parameter such as effective charges. In particular, we clearly identify six bands, two of which we interpret as collective gamma bands.
nucl-thPRC(2018)·14 citations
04
The impact of the surface energy coefficient on the deformation properties of atomic nuclei as predicted by Skyrme energy density functionals
W. Ryssens🇫🇷 · M. Bender🇫🇷 · K. Bennaceur🇫🇷 · P.-H. Heenen🇧🇪 · J. Meyer🇫🇷
In the framework of nuclear energy density functional (EDF) methods, many nuclear phenomena are related to the deformation of intrinsic states. Their accurate modeling relies on the correct description of the change of nuclear binding energy with deformation. The two most important contributions to the deformation energy have their origin in shell effects that are correlated to the spectrum of single-particle states, and the deformability of nuclear matter, that can be characterized by a model-dependent surface energy coefficient a_{surf}. With the goal of improving the global performance of nuclear EDFs through fine-tuning of their deformation properties, the purpose of this study is threefold. First, to analyze the impact of systematic variations of a_{surf} on properties of nuclei; second, to identify observables that can be safely used to narrow down the range of appropriate values of a_{surf} to be targeted in future parameter fits; third, to analyze the interdependence of a_{surf} with other properties of a nuclear EDF. Results for a large variety of relevant observables of deformed nuclei obtained from self-consistent mean-field calculations with a set of purpose-built SLy5sX parameterizations of the Skyrme EDF are correlated with the value of a_{surf}. The three main conclusions are that there is an evident preference for a comparatively low value of a_{surf}, as expected from the performance of existing parameterizations; that the isospin dependence of the surface energy also needs further finetuning in order to describe trends across the chart of nuclei; and that a satisfying simultaneous description of fission barriers and superdeformed states requires a better description of the single-particle spectra. [Note: The abstract has been abbreviated because of length restrictions imposed by the arXiv. See the paper for the full abstract.]
nucl-thPRC(2019)·31 citations
05
Two-dimensional collective Hamiltonian for chiral and wobbling modes II: Electromagnetic transitions
X. H. Wu · Q. B. Chen · P. W. Zhao · S. Q. Zhang · J. Meng
The intraband electromagnetic transitions in the framework of collective Hamiltonian for chiral and wobbling modes are calculated. By going beyond the mean field approximation on the orientations of rotational axis, the collective Hamiltonian provides the descriptions on both yrast band and collective excitation bands. For a system with one $h_{11/2}$ proton particle and one $h_{11/2}$ neutron hole coupled to a triaxial rotor ( $γ = - 3 0^{\circ}$ ), the intraband electromagnetic transitions given by the one-dimensional and two-dimensional collective Hamiltonian are compared to the results by the tilted axis cranking approach and particle rotor model. Compared with the tilted axis cranking approach, the electromagnetic transitions given by the collective Hamiltonian have a better agreement with those by the particle rotor model, due to the consideration of the quantum fluctuations.
nucl-thnucl-exPRC(2018)·20 citations
06
Two-neutrino double electron capture on $^{124}$ Xe based on an effective theory and the nuclear shell model
E. A. Coello Pérez🇩🇪 · J. Menéndez🇯🇵 · A. Schwenk🇩🇪
We study the two-neutrino double electron capture on $^{124}$ Xe based on an effective theory (ET) and large-scale shell model calculations, two modern nuclear structure approaches that have been tested against Gamow-Teller and double-beta decay data. In the ET, the low-energy constants are fit to electron capture and $β^{-}$ transitions around xenon. For the nuclear shell model, we use an interaction in a large configuration space that reproduces the spectroscopy of nuclei in this mass region. For the dominant transition to the $^{124}$ Te ground state, we find half-lives $T_{1/2}^{2 ν ECEC} = (1.3 - 18) \times 1 0^{22}$ y for the ET and $T_{1/2}^{2 ν ECEC} = (0.43 - 2.9) \times 1 0^{22}$ y for the shell model. The ET uncertainty leads to a half-life almost entirely consistent with present experimental limits and largely within the reach of ongoing experiments. The shell model half-life range overlaps with the ET, but extends less beyond current limits. Our findings thus suggest that the two-neutrino double electron capture on $^{124}$ Xe has a good chance to be discovered by ongoing or future experiments. In addition, we present results for the two-neutrino double electron capture to excited states of $^{124}$ Te.
nucl-thnucl-exPLB(2019)·35 citations
07
Neutron star universal relations with microscopic equations of state
J.-B. Wei🇮🇹 · A. Figura🇮🇹 · G. F. Burgio🇮🇹 · H. Chen🇨🇳 · H.-J. Schulze (INFN Sezione di Catania)🇮🇹
We calculate neutron star's moment of inertia and deformabilities using various microscopic equations of state for nuclear and hybrid star configurations. Correlations between the various observables are examined and we confirm several universal relations. We focus in particular on the constraints for the neutron star radii imposed by a determination of the average tidal deformability of the binary neutron star system GW170817. We find compatible radii between 12 and 13 kilometers and identify the suitable equations of state.
↳ astro-ph.HEnucl-thJ.Phys.G(2019)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE

Possible determination of high-lying single particle components with (p,d) reactions

The enhancement of v4​ in nuclear collisions at the highest densities signals a first order phase transition

Symmetry Conserving Configuration Mixing description of odd mass nuclei

The impact of the surface energy coefficient on the deformation properties of atomic nuclei as predicted by Skyrme energy density functionals

Two-dimensional collective Hamiltonian for chiral and wobbling modes II: Electromagnetic transitions

Two-neutrino double electron capture on 124Xe based on an effective theory and the nuclear shell model

Neutron star universal relations with microscopic equations of state

Affiliations

The enhancement of $v_{4}$ in nuclear collisions at the highest densities signals a first order phase transition

Two-neutrino double electron capture on $^{124}$ Xe based on an effective theory and the nuclear shell model