Nuclear Theory·nucl-th

Monday·December 9, 2019

11 papers—8 primary·3 cross-listed

01
[Submitted on 5 Dec 2019]
Interference Effects for $0 ν β β$ Decay in the Left-Right Symmetric Model
Fahim Ahmed🇺🇸 · Mihai Horoi🇺🇸
Various mechanisms may contribute to neutrinoless double beta decay in the left-right symmetric model. The interference between these mechanisms also contribute to the overall decay rate. The analysis of the contributions of these interference terms is important for disentangling different mechanisms. In the present paper we study interference effects contributing to the decay rate for neutrinoless double- $β$ decay in the left-right symmetric model. The numerical values for maximum interference for several nuclides are calculated. It is observed that, for most of the interference terms, the contribution is smaller than 20 $%$ for all the nuclei considered in the study. However, the interference between the mass mechanisms (light and heavy) and $η$ mechanism is observed to be in the range 30 $%$ -50 $%$ . The variation of the interference effect with the $Q$ values is also studied.
Comments:
13 pages, 11 figures, Results updated and edited to match published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1912.02850 [pdf]
PRC(2020)·12 citations
02
[Submitted on 6 Dec 2019]
Microscopic cluster study of the 10Be and 11Be nuclei
Pierre Descouvemont · Naoyuki Itagaki
We use a microscopic multicluster model to investigate the structure of $^{10}$ Be and of $^{11}$ Be. These nuclei are described by $α + α + n + n$ and $α + α + n + n + n$ configurations, respectively, within the Generator Coordinate Method (GCM). The 4- and 5-body models raise the problem of a large number of generator coordinates (6 for $^{10}$ Be and 9 for $^{11}$ Be), which requires specific treatment. We address this issue by using the Stochastic Variational Method (SVM), which is based on an optimal choice of the basis functions, generated randomly. The model provides good energy spectra for low-lying states of both nuclei. We also compute rms radii and densities, as well as electromagnetic transition probabilities. We analyze the structure of $^{10}$ Be and of $^{11}$ Be by considering energy curves, where one of the generator coordinates is fixed during the minimization procedure.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1912.03002 [pdf]
PTEP·18 citations
03
[Submitted on 6 Dec 2019]
Sequential Heavy Ion Double Charge Exchange Reactions and the Link to Double $β$ -decay
Jessica I.Bellone · Stefano Burrello · Maria Colonna · José-Antonio Lay · Horst Lenske
Heavy ion double charge exchange reactions are described by sequential meson-exchange, corresponding to a double single charge exchange (DSCE) reaction mechanism. The theoretical formulation is discussed. The fully quantum mechanical distorted wave 2-step calculations are shown to be reproduced very well by approximating the intermediate propagator by its pole part. The role of ion-ion elastic interactions is discussed. As a first application, calculations are performed for the reaction $^{40}$ Ca $(^{18}$ O $,^{18}$ Ne $)^{40}$ Ar at 15 AMeV. Results are compared to the data measured at LNS by the NUMEN Collaboration. The common aspects of DSCE reactions and double $β$ - decay are discussed by a detailed comparison of the respective nuclear matrix elements (NME).
Comments:
submitted to Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.03043 [pdf]
3 citations
04
[Submitted on 6 Dec 2019]
Volution of nuclear spin-orbit splittings with Skyrme functional SAMi-T
Shihang Shen · Gianluca Colò · Xavier Roca-Maza
A new Skyrme functional has been developed with tensor term guided by ab initio relativistic Brueckner-Hartree-Fock (RBHF) studies on neutron-proton drops. Instead of extracting information on the tensor force from experimental single-particle energy splittings, the RBHF calculations do not contain beyond mean-field effects such as particle-vibration coupling and therefore the information on the tensor force can be obtained without ambiguities. The new functional gives a good description of nuclear ground-state properties as well as various giant resonances. The description for the evolution of single-particle energy splittings is also improved by the new functional.
Comments:
3 pages, 2 figures, IV International Conference on Nuclear Structure and Dynamics (NSD2019)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.03050 [pdf]
EPJ Web Conf.(2019)·0 citations
05
[Submitted on 6 Dec 2019]
Rearrangement term in the nonlocal folding model of the nucleon optical potential
Doan Thi Loan · Dao T. Khoa · Nguyen Hoang Phuc
Based on the mean-field determination of the single-particle energy in nuclear matter that contains naturally a rearrangement term (RT) implied by the Hugenholtz-van Hove theorem, the folding model of the nucleon optical potential (OP) is extended to take into account the RT using the effective, density dependent CDM3Yn interaction. With the exchange part of the nucleon folded OP treated exactly in the Hartree-Fock manner, a compact nonlocal version of the folding model is suggested in the present work to determine explicitly the isospin-dependent, nonlocal central term of the nucleon OP. To solve the optical model (OM) equation with a complex nonlocal OP, the calculable $R$ -matrix method is used to analyse the elastic neutron and proton scattering on $^{40, 48}$ Ca, $^{90}$ Zr, and $^{208}$ Pb targets at low energies. The inclusion of the RT into the folding model calculation of the nonlocal nucleon OP was shown to be essential for the overall good OM description of elastic nucleon scattering. To validate the nonlocal version of the folding model, the OM results given by the nonlocal folded nucleon OP are also compared with those given by the global parametrization of the nonlocal OP using the analytical nonlocal form factor suggested by Perey and Buck.
Comments:
Accepted for publication in J. Phys. G: Nuclear and Particle Physics
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1912.03061 [pdf]
J.Phys.G(2020)·15 citations
06
[Submitted on 6 Dec 2019]
Investigation of interaction of circularly and linearly polarized photon beams with polarized 3He target
H. Witała🇵🇱 · J. Golak🇵🇱 · R. Skibiński🇵🇱 · K. Topolnicki🇵🇱 · V. Urbanevych🇵🇱
Photodisintegration of polarized 3He by linearly or circularily polarized photons offers a rich choice of observables which can be calculated with high precision using a rigorous scheme of three-nucleon Faddeev equations. Using the (semi)phenomenological AV18 nucleon-nucleon potential combined with the Urbana IX three-nucleon force we investigate sensitivity of 3He photodisintegration observables to underlying currents taken in the form of a single-nucleon current supplemented by two-body contributions for $π$ - and $ρ$ -meson exchanges or incorporated by the Siegert theorem. Promising observables to be measured for two- and three-body fragmentation of 3He are identified. These observables form a challenging test ground for consistent forces and currents being under derivation within the framework of chiral perturbation theory. For thre-body 3He photodisintegration several kinematicaly complete configurations, including SST and FSI, are also discussed.
Comments:
25 pages, 10 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.03122 [pdf]
PRC(2020)·1 citation
07
[Submitted on 6 Dec 2019]
Proton-proton momentum correlation function as a probe of the high momentum tail of the nucleon momentum distribution
Gao-Feng Wei🇨🇳 · Xi-Guang Cao🇨🇳 · Qi-Jun Zhi🇨🇳 · Xin-Wei Cao🇨🇳 · Zheng-Wen Long🇨🇳
Within an improved transport model, we examine effects of the high momentum tail of the nucleon momentum distribution induced by short-range correlations on the proton-proton momentum correlation function in $^{197}$ Au+ $^{197}$ Au collisions at 400 MeV/nucleon. It is found that the proton-proton momentum correlation function from preequilibrium emissions responds sensitively to the presence as well as fraction of nucleons in the high momentum tail of the nucleon momentum distribution, but is almost robustly insensitive to other factors including the symmetry energy and the uncertainty of cutoff value of nucleon effective high momentum. In terms of the sensitivity and clearness, we propose that the proton-proton momentum correlation function from preequilibrium emissions can be as an effective probe of the high momentum tail of the nucleon momentum distribution.
Comments:
7 pages, 6 figures. Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1912.03165 [pdf]
PRC(2020)·6 citations
08
[Submitted on 6 Dec 2019]
Proxy-SU(3) symmetry for heavy deformed nuclei: nuclear spectra
D. Bonatsos · I.E. Assimakis · A. Martinou · S. K. Peroulis · S. Sarantopoulou · N. Minkov
The systematics of experimental energy differences between the levels of the ground state band and the gamma-1 band in even-even nuclei are studied as a function of the angular momentum L, demonstrating a decrease of the energy differences with increasing L, in contrast to what is seen in vibrational, gamma-unstable, and triaxial nuclei. After a short review of the relevant predictions of several simple collective models, it is shown that this decrease is caused in the framework of the proxy-SU(3) scheme by the same three-body and/or four body operators which break the degeneracy between the ground state band and the gamma-1 band, predicting in parallel the correct form of odd-even staggering within the gamma-1 bands.
Comments:
13 pages, 3 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1912.03293 [pdf]
Bulg.J.Phys.(2019)·5 citations
09
[Submitted on 5 Dec 2019] (cross-list from astro-ph.HE)
Crystallization of the outer crust of a non-accreting neutron star
A. F. Fantina🇫🇷 · S. De Ridder🇧🇪 · N. Chamel🇧🇪 · F. Gulminelli🇫🇷
The interior of a neutron star (NS) is usually assumed to be made of cold catalyzed matter. However, the outer layers are unlikely to remain in full equilibrium during the formation of the star and its cooling, especially after crystallization. We study the cooling and equilibrium composition of the outer layers of a NS down to crystallization. Here the impurity parameter, usually a free parameter in cooling simulations, is calculated self-consistently using a microscopic model for which a unified equation of state has recently been determined. We follow the evolution of the nuclear distributions of the multi-component Coulomb liquid plasma (MCP) fully self-consistently, adapting a general formalism originally developed for the description of supernova cores. We calculate the impurity parameter at the crystallization as determined in the one-component plasma (OCP) approximation. Our analysis shows that the sharp changes in composition obtained in the OCP approximation are smoothed out when a full nuclear distribution is allowed. The Coulomb coupling parameter at melting is found to be reasonably close to the canonical value of 175, except for specific pressures for which supercooling occurs in the OCP approximation. Our MCP treatment leads to non-monotonic variations of the impurity parameter with pressure. Its values can change by several orders of magnitude reaching about 50, suggesting that the crust may be composed of an alternation of pure (highly conductive) and impure (highly resistive) layers. The results presented here complement the recent unified equation of state obtained with the same model. Our self-consistent approach to hot MCP shows that the presence of impurities in the outer crust of a NS is non-negligible and may have a sizeable impact on transport properties. In turn, this may have important implications for the cooling of NS and their magneto-rotational evolution.
Comments:
15 pages, 8 figures, accepted for publication in Astronomy and Astrophysics
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1912.02849 [pdf]
Astron.Astrophys.(2020)·48 citations
10
[Submitted on 5 Dec 2019] (cross-list from nucl-ex)
Electromagnetic properties of $^{21}$ O for benchmarking nuclear Hamiltonians
S. Heil · M. Petri · K. Vobig · D. Bazin · J. Belarge · P. Bender · B. A. Brown · R. Elder · B. Elman · A. Gade · T. Haylett · J. D. Holt and 16 other authors
The structure of exotic nuclei provides valuable tests for state-of-the-art nuclear theory. In particular electromagnetic transition rates are more sensitive to aspects of nuclear forces and many-body physics than excitation energies alone. We report the first lifetime measurement of excited states in $^{21}$ O, finding $τ_{1/ 2^{+}} = 42 0_{- 32}^{+ 35} (stat)_{- 12}^{+ 34} (sys)$ \,ps. This result together with the deduced level scheme and branching ratio of several $γ$ -ray decays are compared to both phenomenological shell-model and ab initio calculations based on two- and three-nucleon forces derived from chiral effective field theory. We find that the electric quadrupole reduced transition probability of $B (E2; 1/ 2^{+} \to 5/ 2_{g.s.}^{+}) = 0.7 1_{- 0.06 - 0.06}^{+ 0.07 + 0.02}$ ~e $^{2}$ fm $^{4}$ , derived from the lifetime of the $1/ 2^{+}$ state, is smaller than the phenomenological result where standard effective charges are employed, suggesting the need for modifications of the latter in neutron-rich oxygen isotopes. We compare this result to both large-space and valence-space ab initio calculations, and by using multiple input interactions we explore the sensitivity of this observable to underlying details of nuclear forces.
Comments:
23 pages, 3 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1912.02884 [pdf]
PLB(2020)·12 citations
11
[Submitted on 6 Dec 2019] (cross-list from hep-th)
Exact Multi-Instanton Solutions to Selfdual Yang-Mills Equation on Curved Spaces
Jun Nian🇺🇸 · Yachao Qian🇺🇸
We find exact multi-instanton solutions to the selfdual Yang-Mills equation on a large class of curved spaces with $S O (3)$ isometry, generalizing the results previously found on $R^{4}$ . The solutions are featured with explicit multi-centered expressions and topological properties. As examples, we demonstrate the approach on several different curved spaces, including the Einstein static universe and $R \times$ dS $_{3}^{E}$ , and show that the exact multi-instanton solutions exist on these curved backgrounds.
Comments:
6 pages, 4 figures; V2: published version, more discussions added
Subjects:
High Energy Physics — Theory (hep-th); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
1912.03299 [pdf]
Int.J.Mod.Phys.A(2021)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE