Nuclear Theory·nucl-th

Wednesday·January 8, 2020

15 papers—8 primary·7 cross-listed

01
[Submitted on 7 Jan 2020]
Exploring two-neutron halo formation in the ground-state of $^{29}$ F within a three-body model
Jagjit Singh · J. Casal · W. Horiuchi · L. Fortunato · A. Vitturi
Background $:$ The $^{29}$ F system is located at the lower-N boundary of the "island of inversion" and is an exotic, weakly bound system. Little is known about this system beyond its two-neutron separation energy ( $S_{2 n}$ ) with large uncertainties. A similar situation is found for the low-lying spectrum of its unbound binary subsystem $^{28}$ F. Purpose $:$ To investigate the configuration mixing, matter radius and neutron-neutron correlations in the ground state of $^{29}$ F within a three-body model, exploring the possibility of $^{29}$ F to be a two-neutron halo nucleus. Method $:$ The $^{29}$ F ground-state wave function is built within the hyperspherical formalism by using an analytical transformed harmonic oscillator basis. The Gogny-Pires-Tourreil (GPT) nn interaction with central, spin-orbit and tensor terms is employed in the present calculations, together with different core $+ n$ potentials constrained by the available experimental information on $^{28}$ F. Results $:$ The $^{29}$ F ground-state configuration mixing and its matter radius are computed for different choices of the $^{28}$ F structure and $S_{2 n}$ value. The admixture of d-waves with pf components are found to play an important role, favoring the dominance of dineutron configurations in the wave function. Our computed radii show a mild sensitivity to the $^{27}$ F $+ n$ potential and $S_{2 n}$ values. The relative increase of the matter radius with respect to the $^{27}$ F core lies in the range 0.1-0.4 fm depending upon these choices. Conclusions $:$ Our three-body results for $^{29}$ F indicate the presence of a moderate halo structure in its ground state, which is enhanced by larger intruder components. This finding calls for an experimental confirmation.
Comments:
8 pages, 4 figures, Final version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2001.01849 [pdf]
PRC(2020)·33 citations
02
[Submitted on 7 Jan 2020]
Interpretation of normal-deformed bands in 167Lu
Azam Kardan · Ingemar Ragnarsson · B. Gillis Carlsson · Hai-Liang Ma
With the aim to get a general understanding of rotational bands in the deformed rare-earth region or in deformed nuclei in general, the observed normal-deformed rotational structures in $^{167}$ Lu are interpreted within the unpaired and paired cranked Nilsson-Strutinsky formalisms, CNS and CNSB. Particular attention is devoted to the band crossings. For this nucleus with the Fermi surface high up in the $h_{11/2}$ shell, we conclude that except for the paired AB and BC crossings in configurations with an even and odd number of $i_{13/2}$ neutrons, respectively, the observed band crossings can be understood within the unpaired formalism. Especially, it means that above the AB and BC crossings, the evolution with spin is described as a gradual alignment of the spin vectors of the particles outside closed shells. Consequently, the configurations can be characterized by the number of particles occupying open $j$ -shells or groups of $j$ -shells. In the present study, we revise the interpretation of some experimental bands and also the nature of the crossings while some previous configuration assignments are confirmed.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2001.01922 [pdf]
PRC(2020)·8 citations
03
[Submitted on 7 Jan 2020]
PairDiag: an exact diagonalization program for solving general pairing Hamiltonians
Xiaoyu Liu · Chong Qi
We present a program for solving exactly the general pairing Hamiltonian based on diagonalization. The program generates the seniority-zero shell-model-like basis vectors via the `01' inversion algorithm. The Hamiltonian matrix is constructed in that seniority-zero space. The program evaluates all non-zero elements of the Hamiltonian matrix "on the fly" using the scattering operator and the search algorithm that act on the generated basis. The matrix is diagonalized by using the iterative Lanczos algorithm. The program thus developed, PairDiag, can calculate efficiently the ground-state eigenvalue and eigenvector of any pairing Hamiltonian. The program can be easily implemented to replace the BCS approximation in standard self-consistent mean-field calculations. The code is parallelized using OpenMP. For larger systems with dimension around 10 $^{8 - 9}$ , the calculation can be done within a day on standard desktop computers.
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2001.01978 [pdf]
Comput.Phys.Commun.(2021)·8 citations
04
[Submitted on 7 Jan 2020]
Fission rate of excited nuclei at variable friction in the energy diffusion regime
Maria Chushnyakova · Igor Gontchar
Presently, it is well established that fission of excited nuclei is a dynamical process being a subject of fluctuations and dissipation. In the literature, there are indications that, at the compact nucleus shapes, the strength of nuclear friction is significantly reduced in comparison with the prediction of the one-body approach. Thus, one can expect that at small deformations the nuclear fission process occurs in the so-called "energy diffusion regime". The purpose of our present work is to compare an approximate analytical formula for the fission rate in this regime with the quasistationary numerical rate which is exact within the statistical errors. Our calculations demonstrate relatively good agreement between these two rates provided the friction parameter is deformation independent. If one accounts for its deformation dependence, the agreement becomes significantly poorer.
Comments:
INPC2019 contribution
Subjects:
Nuclear Theory (nucl-th); physics.chem-ph (physics.chem-ph)
arXiv:
2001.02051 [pdf]
J.Phys.Conf.Ser.(2020)·0 citations
05
[Submitted on 7 Jan 2020]
Two ways for numerical solution of the Kramers problem for spatial diffusion over an edge-shaped barrier
Maria Chushnyakova · Igor Gontchar · Alexander Zakharov · Natalya Khmyrova
Thermal decay rate over an edge-shaped barrier at high dissipation is studied numerically through the computer modeling. Two sorts of the stochastic Langevin type equations are applied: (i) the Langevin equations for the coordinate and conjugate momentum (LEqp, the phase space diffusion) and (ii) the reduced Langevin equation (RLE, the spatial diffusion, overdamped motion). The latter method is much faster and self-similar; however, one can doubt about its applicability in the case of an edge-shaped barrier with a discontinuous force. The reason is that a formal condition of the applicability of the RLE is not fulfilled since the curvature of the potential profile at the barrier is equal to infinity. The present numerical study demonstrates that, for large friction, the decay rate calculated using the RLE agrees with the rate resulting from the more exact LEqp. Moreover, it turns out that the influence of the position of the absorbing border is similar to the case of harmonic potential known in the literature.
Comments:
Dynamics-2019 Second contribution
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2001.02080 [pdf]
J.Phys.Conf.Ser.(2020)·0 citations
06
[Submitted on 7 Jan 2020]
Accuracy of the analytical escape rate for a cusp barrier in the overdamping regime
Alexander Zakharov · Maria Chushnyakova · Igor Gontchar
For the first time, the accuracy of the approximate analytical Kramers formula for the thermal decay rate over a cusp barrier, $R_{K}$ , is checked numerically for the overdamping regime. The numerical quasistationary rate, $R_{D}$ , which is believed to be exact within the statistical errors is evaluated by means of computer modeling of the stochastic Langevin-type dynamical equations. The agreement between $R_{K}$ and $R_{D}$ significantly depends upon the friction strength and the height of the barrier in comparison to the thermal energy. The difference between $R_{K}$ and $R_{D}$ decreases with the dimensionless damping parameter $ϕ$ , however, does not become smaller than 10-20%. The unexpected growth of the difference between $R_{K}$ and $R_{D}$ with the governing parameter is observed.
Comments:
Dynamics-2019 First contribution
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2001.02087 [pdf]
J.Phys.Conf.Ser.(2020)·0 citations
07
[Submitted on 7 Jan 2020]
Frame dependence of transition form factors in light-front dynamics
Meijian Li🇺🇸
We study the radiative transitions between vector and pseudoscalar quarkonia in the light-front Hamiltonian approach, and investigate the effects of using different current component and different reference frames. In practical calculations with truncated Fock spaces, transition form factors may acquire current component dependence and frame dependence, and such dependences could serve as a measure for the Lorentz symmetry violation. We suggest using the transverse current with $m_{j} = 0$ state of the vector meson, since this procedure employs the dominant spin components of the light-front wavefunctions and is more robust in practical calculations. We calculate the transition form factor between vector and pseudoscalar quarkonia and investigate the frame dependence with light-front wavefunctions calculated from the valence Fock sector. We suggest using frames with minimal longitudinal momentum transfer for calculations in the valence Fock sector, namely the Drell-Yan frame for the space-like region and a specific longitudinal frame for the timelike region; at $q^{2} = 0$ these two frames give the same result.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2001.02108 [pdf]
PoS(2020)·3 citations
08
[Submitted on 7 Jan 2020]
Strangeness and light fragment production at high baryon density
D. Blaschke🇵🇱 · G. Röpke🇷🇺 · Yu. Ivanov🇷🇺 · M. Kozhevnikova🇷🇺 · S. Liebing🇩🇪
We discuss medium effects on light cluster production in the QCD phase diagram within a generalized Beth-Uhlenbeck (GBU) approach by relating Mott transition lines to those for chemical freeze-out. We find that in heavy-ion collisions at highest energies provided by the LHC light cluster abundances should follow the statistical model because of low baryon densities. At low energies in the nuclear fragmentation region, where the freeze-out interferes with the liquid-gas phase transition, selfenergy and Pauli blocking effects are important. At intermediate energies the HADES, FAIR and NICA experiments can give new information. The GBU approach provides new insights to strange hadron production in this energy domain for explaining the "horn" effects.
Comments:
8 pages, 5 figures, Contribution to the Proceedings of the 18th International Conference on 'Strangeness in Quark Matter' (SQM-2019), Bari, Italy, 10-15 June, 2019
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2001.02156 [pdf]
Springer Proc.Phys.(2020)·5 citations
09
[Submitted on 6 Jan 2020] (cross-list from hep-ph)
Ab initio calculations of reactor antineutrino fluxes with exact lepton wave functions
Dong-Liang Fang🇨🇳 · Yu-Feng Li🇨🇳 · Di Zhang🇨🇳
New \textit{ab initio} calculations of the isotopic reactor antineutrino fluxes are provided with exact numerical calculations of the lepton wave functions, assuming all the decay branches are allowed GT transitions. We illustrate that the analytical Fermi function and finite size effect each could have the largest spectral deviation of $O (10%)$ , whereas the effect of their combination could result in spectral deviations at the level of 5%-10%. Meanwhile, we also find that several forms of the extended charge distributions have negligible effects on the spectral variation. Using the state-of-the-art nuclear databases, compared to usual \textit{ab initio} calculations using the analytical single beta decay spectrum, our new calculation shows sizable but opposite spectral deviations at the level of 2%-4% for the cumulative antineutrino and electron energy spectra which may partially contribute to the observed spectral excess in the high energy antineutrino range. Finally we observe that the {bias} of analytical beta decay spectrum approximation is rather universal for all the four fissionable isotopes.
Comments:
17 pages, 5 figures, version to appear in PLB
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2001.01689 [pdf]
PLB(2021)·7 citations
10
[Submitted on 7 Jan 2020] (cross-list from physics.atom-ph)
Nuclear magnetic moments of francium 207-213 from precision hyperfine comparisons
B. M. Roberts · J. S. M. Ginges
We report a fourfold improvement in the determination of nuclear magnetic moments for neutron-deficient isotopes of francium-207--213, reducing the uncertainties from 2% for most isotopes to 0.5%. These are found by comparing our high-precision calculations of hyperfine structure constants for the ground states with experimental values. In particular, we show the importance of a careful modeling of the Bohr-Weisskopf effect, which arises due to the finite nuclear magnetization distribution. This effect is particularly large in Fr and until now has not been modeled with sufficiently high accuracy. An improved understanding of the nuclear magnetic moments and Bohr-Weisskopf effect are crucial for benchmarking the atomic theory required in precision tests of the standard model, in particular atomic parity violation studies, that are underway in francium.
Comments:
Adds supplementary material
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
arXiv:
2001.01907 [pdf]
PRL(2020)·15 citations
11
[Submitted on 7 Jan 2020] (cross-list from nucl-ex)
Overview of experimental critical point search
Tobiasz Czopowicz🇵🇱
The existence and location of the QCD critical point is an object of vivid experimental and theoretical studies. Rich and beautiful data recorded by experiments at SPS and RHIC allow for a systematic search for the critical point - the search for a non-monotonic dependence of various correlation and fluctuation observables on collision energy and size of colliding nuclei.
Comments:
The 18th International Conference on Strangeness in Quark Matter (SQM 2019) proceedings, 8 pages, 8 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2001.01944 [pdf]
Springer Proc.Phys.(2020)·3 citations
12
[Submitted on 7 Jan 2020] (cross-list from hep-ph)
Dynamically generated hadron resonances
Tetsuo Hyodo🇯🇵
Recent developments in hadron spectroscopy triggers the discussion on various exotic configurations beyond the simple three-quark state for baryons and quark-anti-quark pair for mesons. In particular, the states observed near a two-hadron threshold are often regarded as candidates of hadronic molecules, which are made of constituent hadrons and dynamically generated by the hadronic interactions. However, identification of the hadronic molecules involves several subtle difficulties which are often overlooked or underestimated. Here we summarize these subtleties and present a promising approach to distinguish the dynamically generated states from others using observable quantities.
Comments:
8 pages, Talk given at XVIII International Conference on Hadron Spectroscopy and Structure (Hadron 2019), Aug. 16-21, 2019, Guilin, China
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2001.01950 [pdf]
1 citation
13
[Submitted on 7 Jan 2020] (cross-list from hep-ph)
A proton imagining via double parton scattering
Matteo Rinaldi🇮🇹
In this contribution we discuss the main outcomes of our studies on the so called double parton distribution functions (dPDFs), accessible quantities in high energy proton-proton and proton nucleus collisions, in double parton scattering processes (DPS). These new distributions are almost unknown, nevertheless they encode information on how partons inside a proton are correlated among each other. Double PDFs represent a new tool to explore the three dimensional partonic structure of hadrons. Here, we show results obtained from calculations of dPFDs. In particular we focus our attention on the impact of double correlations in experimental observables by showing how the latter could be studied in the next LHC run. We also discuss how the present knowledge on a peculiar experimental observable could unveil new information on the transverse proton structure
Comments:
5 pages, 2 figures. Talk presented at Light-Cone 2019 - QCD on the light cone: from hadrons to heavy ions - LC2019. 16-20 September 2019. Ecole Polytechnique, Palaiseau, France. To be published in the conference proceedings
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2001.01977 [pdf]
PoS(2020)·0 citations
14
[Submitted on 7 Jan 2020] (cross-list from nucl-ex)
Nuclear physics uncertainties in neutrino-driven, neutron-rich supernova ejecta
J. Bliss (Institut fur Kernphysik, Technische Universitat Darmstadt, Germany) · A. Arcones (Institut fur Kernphysik, Technische Universitat Darmstadt, Germany and GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt, Germany) · F. Montes (National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI, USA and Joint Institute for Nuclear Astrophysics) · J. Pereira (National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI, USA and Joint Institute for Nuclear Astrophysics)
Neutrino-driven ejecta in core collapse supernovae (CCSNe) offer an interesting astrophysical scenario where lighter heavy elements between Sr and Ag can be synthesized. Previous studies emphasized the important role that ( $α, n$ ) reactions play in the production of these elements, particularly in neutron-rich and alpha-rich environments. In this paper, we have investigated the sensitivity of elemental abundances to specific ( $α, n$ ) reaction-rate uncertainties under different astrophysical conditions. Following a Monte Carlo nucleosynthesis study with over 36 representative astrophysical wind conditions, we have identified the most important reactions based on their impact on the final elemental abundances. Experimental studies of these reactions will reduce the nucleosynthesis uncertainties and make it possible to use observations to understand the origin of lighter heavy elements and the astrophysical conditions where they are formed.
Subjects:
Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2001.02085 [pdf]
PRC(2020)·47 citations
15
[Submitted on 6 Jan 2020] (cross-list from hep-ph)
Strong decays of the newly observed narrow $Ω_{b}$ structures
Wei Liang🇨🇳 · Qi-Fang Lü🇨🇳
Motivated by the newly observed narrow structures $Ω_{b} (6316)^{-}$ , $Ω_{b} (6330)^{-}$ , $Ω_{b} (6340)^{-}$ , and $Ω_{b} (6350)^{-}$ in the $Ξ_{b}^{0} K^{-}$ mass spectrum, we investigate the strong decays of the low-lying $Ω_{b}$ states within the $^{3} P_{0}$ model systematically. According to their masses and decay widths, the observed $Ω_{b} (6316)^{-}$ , $Ω_{b} (6330)^{-}$ , $Ω_{b} (6340)^{-}$ , and $Ω_{b} (6350)^{-}$ resonances can be reasonably assigned as the $λ -$ mode $Ω_{b} (1 P)$ states with $J^{P} = 1/ 2^{-}, 3/ 2^{-}, 3/ 2^{-}$ , and $5/ 2^{-}$ . Meanwhile, the remaining $P -$ wave state with $J^{P} = 1/ 2^{-}$ should have a rather broad width, which can hardly be observed by experiments. For the $Ω_{b} (2 S)$ and $Ω_{b} (1 D)$ states, our predictions show that these states have relatively narrow total widths and mainly decay into the $Ξ_{b} K ˉ$ , $Ξ_{b}^{'} K ˉ$ and $Ξ_{b}^{' *} K ˉ$ final states. These abundant theoretical predictions may be valuable for searching more excited $Ω_{b}$ states in future experiments.
Comments:
7 pages,4 figures,and 4 tables. Simplify the formalism of the model. Minor modifications. arXiv admin note: text overlap with arXiv:1910.06126 and arXiv:1908.00223
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2001.02221 [pdf]
EPJC(2020)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE