Nuclear Theory·nucl-th

Wednesday·June 21, 2017

15 papers—10 primary·5 cross-listed

01
[Submitted on 19 Jun 2017]
Correlation Energy of Proton-Neutron Subsystem in Valence Orbit
Tomohiro Oishi🇮🇹 · Lorenzo Fortunato🇮🇹
Deuteron correlation energy (DCE) of the valence proton-neutron subsystem is evaluated by utilizing a simple three-body model. We focus on the $^{6}$ Li and $^{18}$ F nuclei assuming the doubly-closed core and the valence proton and neutron. Two interaction models, schematic density-dependent contact (SDDC) and Minnesota potentials, are utilized to describe the proton-neutron interaction. Evaluating DCE, we conclude that the proton-neutron binding in $^{6}$ Li can be stronger than its counterpart of a deuteron in vacuum. On the other hand, in $^{18}$ F, the energetic correlation is remarkably weak, and does not favor the bound, deuteron-like configuration. This significant difference between two systems can be understood from a competition between the proton-neutron kinetic and pairing energies, which are sensitive to the spatial extension of the wave function. This result indicates a remarkable dependence of the deuteron correlation to its environment and the valence orbits.
Comments:
11 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); physics.atm-clus (physics.atm-clus)
arXiv:
1706.06115 [pdf]
0 citations
02
[Submitted on 19 Jun 2017]
Three-body Unitarity with Isobars Revisited
M. Mai🇺🇸 · B. Hu🇺🇸 · M. Doring🇺🇸 · A. Pilloni🇺🇸 · A. Szczepaniak🇺🇸
The particle exchange model of hadron interactions can be used to describe three-body scattering under the isobar assumption. In this study we start from the 3->3 scattering amplitude for spinless particles, which contains an isobar-spectator scattering amplitude. Using a Bethe-Salpeter Ansatz for the latter, we derive a relativistic three-dimensional scattering equation that manifestly fulfills three-body unitarity and two-body unitarity for the sub-amplitudes. This property holds for energies above breakup and also in the presence of resonances in the sub-amplitudes.
Comments:
18 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1706.06118 [pdf]
EPJA(2017)·108 citations
03
[Submitted on 19 Jun 2017]
Multiple Chirality in Nuclear Rotation: A Microscopic View
P. W. Zhao🇺🇸
Covariant density functional theory and three-dimensional tilted axis cranking are used to investigate multiple chirality in nuclear rotation for the first time in a fully self-consistent and microscopic way. Two distinct sets of chiral solutions with negative and positive parities, respectively, are found in the nucleus 106Rh. The negative-parity solutions reproduce well the corresponding experimental spectrum as well as the B(M1)/B(E2) ratios of the transition strengths. This indicates that a predicted positive-parity chiral band should also exist. Therefore, it provides a further strong hint that multiple chirality is realized in nuclei.
Comments:
15 pages, 5 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1706.06127 [pdf]
PLB(2017)·91 citations
04
[Submitted on 20 Jun 2017]
Four-body continuum effects in 11Be+d scattering
Pierre Descouvemont🇧🇪
We present a new reaction model, which permits the description of reactions where both colliding nuclei present a low threshold to breakup. The method corresponds to a four-body extension of the Continuum Discretized Coupled Channel (CDCC) model. We first discuss the theoretical formalism, and then apply the method to 11Be+d scattering at Ecm = 45.5 MeV. The 11Be nucleus and the deuteron are described by 10Be+n and p + n structures, respectively. The model involves very large bases, but we show that an accurate description of elastic-scattering data may be achieved only when continuum states of 11Be and of the deuteron are introduced simultaneously. We also discuss breakup calculations, and show that the cross section is larger for 11Be than for the deuteron. The present theory provides reliable wave functions that may be used in the analysis of (d,p) or (d,n) experiments involving radioactive beams.
Comments:
5 pages, 4 figures, accepted for publication at Physics Letters B
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.06298 [pdf]
PLB(2017)·20 citations
05
[Submitted on 20 Jun 2017]
Improved version of simplified method for including tensor effect in cluster models
N. Itagaki🇯🇵 · A Tohsaki🇯🇵
The tensor contribution can be directly incorporated in the cluster model in a simplified way. In conventional $α$ cluster models, the contribution of the non-central interactions exactly cancels because of the antisymmetrization effect and spatial symmetry of $α$ clusters. The mixing of breaking components of $α$ clusters to take into account the spin-orbit and tensor effects is needed. Previously we proposed a simplified method to include the spin-orbit effect, and also for the tensor part, a simplified model to directly take into account the contribution of the tensor interaction (called SMT) was introduced; however the contribution of the tensor interaction was quite limited. Here we improve SMT, which is called $i$ SMT. Using newly proposed $i$ SMT, the contribution of the tensor interaction in $^{4}$ He is more than $- 40$ MeV, four times larger than the previous version. The method is applied to four- $α$ cluster structure of $^{16}$ O. In $^{16}$ O, the tensor contribution is also large, and this is coming from the finite size effect for the distances among $α$ clusters with a tetrahedral configuration.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.06308 [pdf]
PRC(2018)·24 citations
06
[Submitted on 20 Jun 2017]
Two-nucleon emission in neutrino and electron scattering from nuclei: the modified convolution approximation
I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · T.W. Donnelly🇺🇸
The theoretical formalism of inclusive lepton-nucleus scattering in the two-nucleon emission channel is discussed in the context of a simplified approach, the modified convolution approximation. This allows one to write the 2p2h responses of the relativistic Fermi gas as a folding integral of two 1p1h responses with the energies and momenta transferred to each nucleon. The idea behind this method is to introduce different average momenta for the two initial nucleons in the matrix elements of the two-body current, with the innovation that they depend on the transferred energies and momenta. This method treats exactly the two-body phase space kinematics, and reduces the formulae of the response functions from seven-dimensional integrals over momenta to much simpler three-dimensional ones. The applicability of the method is checked by comparing with the full results within a model of electroweak meson-exchange currents. The predictions are accurate enough, especially in the low-energy threshold region where the average momentum approximation works the best.
Comments:
35 pages, 13 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1706.06377 [pdf]
Annals Phys.(2018)·14 citations
07
[Submitted on 18 Jun 2017]
Onset of $η$ -meson binding in the He isotopes
N. Barnea🇮🇱 · E. Friedman🇺🇸 · A. Gal🇮🇱
The onset of binding $η$ (548) mesons in nuclei is studied in the He isotopes by doing precise $η N N N$ and $η N N N N$ few-body stochastic variational method calculations for two semi-realistic $N N$ potentials and two energy dependent $η N$ potentials derived from coupled-channel models of the $N^{*} (1535)$ nucleon resonance. The energy dependence of the $η N$ subthreshold input is treated self consistently. It is found that a minimal value of the real part of the $η N$ scattering length $a_{η N}$ close to 1 fm is required to bind $η$ mesons in $^{3}$ He, yielding then a few MeV $η$ binding in $^{4}$ He. The onset of $η$ -meson binding in $^{4}$ He requires that Re $a_{η N}$ exceeds 0.7 fm approximately. These results compare well with results of recent $η N N N$ and $η N N N N$ pionless effective field theory calculations. Related optical-model calculations are also discussed.
Comments:
v3 -- 18 pages, 6 figures, 4 tables, and matching the published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1706.06455 [pdf]
NPA(2017)·34 citations
08
[Submitted on 20 Jun 2017]
Sampling General N-Body Interactions with Auxiliary Fields
Christopher Körber🇩🇪 · Evan Berkowitz🇩🇪 · Thomas Luu🇩🇪
We present a general auxiliary field transformation which generates effective interactions containing all possible N-body contact terms. The strength of the induced terms can analytically be described in terms of general coefficients associated with the transformation and thus are controllable. This transformation provides a novel way for sampling 3- and 4-body (and higher) contact interactions non-perturbatively in lattice quantum monte-carlo simulations. We show that our method reproduces the exact solution for a two-site quantum mechanical problem.
Comments:
5 pages, 1 figure and a supplemental Mathematica notebook
Subjects:
Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Lattice (hep-lat)
arXiv:
1706.06494 [pdf]
EPL(2017)·9 citations
09
[Submitted on 20 Jun 2017]
New cluster approach on properties of 8-11Be isotopes with isospin-dependent spin-orbit potential
Mengjiao Lyu🇨🇳 · Zhongzhou Ren🇨🇳 · Hisashi Horiuchi🇯🇵 · Bo Zhou🇯🇵 · Yasuro Funaki🇨🇳 · Gerd Röpke🇩🇪 · Peter Schuck🇫🇷 · Akihiro Tohsaki🇯🇵 · Chang Xu🇨🇳 · Taiichi Yamada🇯🇵
The nonlocalized clustering approach is generalized to 8-11Be isotopes with isospin dependent spin-orbit potential. A new form of the Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function is introduced to provide a correct description for the {\sigma}-binding neutron in 11Be. Systematic calculations for 8-11Be isotopes are performed and results fit well with experimental values. The low energy spectrum of 11Be is also obtained, especially the correct spin-parity 1/2+ is reproduced for the intruder ground state. The exotic neutron halo structure of 11Be is studied by calculations of root-mean-square radii and density distribution. We obtain a large spatial distribution for the last valence neutron of 11Be, which fits the phenomenological extracted value from experimental data. The spectroscopic factor is also calculated and discussed for the 1/2+ ground state of 11Be.
Comments:
14 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.06538 [pdf]
6 citations
10
[Submitted on 20 Jun 2017]
Extending pairing energy density functional using pairing rotational moments of inertia
Nobuo Hinohara🇯🇵
The pairing energy density functionals (EDFs) that include the spatial derivative and kinetic terms of the pair densities are discussed. The coupling constants of the pairing EDF are adjusted to reproduce the experimental pairing rotational moment of inertia, and the pair-density derivative terms are shown to systematically improve the values of the pairing rotational moments of inertia in Sn and Pb isotopes. It is pointed out that the conventional average pairing gaps overestimate the experimental odd-even mass staggering in the presence of the pair-density derivative terms.
Comments:
19 pages, 7 figures, submitted to J. Phys. G
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.06547 [pdf]
J.Phys.G(2018)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE