Nuclear Theory·nucl-th

Thursday·June 18, 2020

11 papers—5 primary·6 cross-listed

01
[Submitted on 16 Jun 2020]
Is perturbative study of ground-state correlations valid?
Mitsuru Tohyama
Perturbative approaches have often been used to include the effects of ground-state correlations in extended theories of the random-phase approximation. Validity of such approaches is investigated for a solvable model where comparison with exact solutions can be made. It is pointed out that there is a case where perturbative approaches give good results in spite of the fact that interaction strength is far beyond a perturbative region.
Comments:
6 pages,11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.09561 [pdf]
0 citations
02
[Submitted on 17 Jun 2020]
Study of Charge Radii with Neural Networks
Di Wu🇨🇳 · C.L. Bai🇨🇳 · H. Sagawa🇯🇵 · H.Q. Zhang🇨🇳
A feed-forward neural network model is trained to calculate the nuclear charge radii. The model trained with input data set of proton and neutron number $Z, N$ , the electric quadrupole transition strength $B (E 2)$ from the first excited 2 $^{+}$ state to the ground state, together with the symmetry energy. The model reproduces well not only the isotope dependence of charge radii, but also the kinks of charge radii at the neutron magic numbers $N = 82$ for Sn and Sm isotopes, and also $N = 126$ for Pb isotopes. The important role of $B (E 2)$ value is pointed out to reproduce the kink of the isotope dependence of charge radii in these nuclei. Moreover, with the inclusion of the symmetry energy term in the inputs, the charge radii of Ca isotopes are well reproduced. This result suggests a new correlation between the symmetry energy and charge radii of Ca isotopes. The Skyrme HFB calculation is performed to confirm the existence of this correlation in a microscopic model.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.09677 [pdf]
PRC(2020)·84 citations
03
[Submitted on 17 Jun 2020]
On a quasi-bound state in the $K^{-} d$ system caused by strong interactions
N.V. Shevchenko🇨🇿
It was found that $N N$ potential could influence the results of the quasi-bound state search in the $K^{-} d$ system, where the corresponding pole is situated close to the threshold. Three-body Faddeev-type calculations of the $K ˉ N N - π Σ N$ system performed with a new model of nucleon-nucleon interaction predict the existence of the quasi-bound $K^{-} d$ state caused by strong interactions. Its binding energy is small ( $1 - 2$ MeV), while the width is comparable with the width of the $K^{-} pp$ quasi-bound state ( $40 - 60$ MeV).
Comments:
8 pages, 2 figures, 4 tables; v2: minor changes in Section 2, additional information about the NN potential in Section 3; accepted to the special issue of Few-Body Systems journal "New Trends in Hadron Physics: a Few-Body Perspective"
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.09800 [pdf]
Few Body Syst.(2020)·8 citations
04
[Submitted on 17 Jun 2020]
Properties of a separable representation of optical potentials
Michael Quinonez · Linda Hlophe · Filomena Nunes
Background: Separable interactions have a long history in nuclear physics. In the last few years, separable expansions have been used to represent the optical potential between a nucleon (proton or neutron) and a target. Purpose: We explore the non-local properties of these separable optical potentials as well as their convergence behavior. Method: For a couple of cases, we use the generalized Ersnt-Shakin-Thaler scheme to generate separable interactions starting from local optical potentials. We study the variation of the interaction with energy range and rank. Results: We find that, overall the off-diagonal behavior of the converged separable interaction deviates from the Gaussian form assumed by Perey and Buck. However, in the region surrounding the maximum depth the Gaussian form works quite well. Focusing on this region, we study potentials describing neutron elastic scattering on $^{16}$ O and $^{48}$ Ca for beam energies in the range of $E =$ 10-50 MeV and explore several measures of non-locality of the separable interactions. Conclusions: When the energy range considered for generating the separable interaction is $0 \leq E_{r an g e} \leq 50$ MeV, the resulting non-locality is large and target dependent. Contrarily, the nonlocality obtained including larger energy ranges in the separable procedure is independent of the target and other details of the original local potential. We find that, even when including in the expansion many support points with energy ranges $0 \leq E_{r an g e} \leq 2400$ MeV, the resulting potential retains non-local behavior. Connections with microscopic optical potentials as well as other transformations used in the nucleon-nucleon domain are made.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.09926 [pdf]
PRC(2020)·2 citations
05
[Submitted on 17 Jun 2020]
X(3872) Transport in Heavy-Ion Collisions
Biaogang Wu🇺🇸 · Xiaojian Du🇩🇪 · Matthew Sibila🇺🇸 · Ralf Rapp🇺🇸
The production of the $X (3872)$ particle in heavy-ion collisions has been contemplated as an alternative probe of its internal structure. To investigate this conjecture, we perform transport calculations of the $X (3872)$ through the fireball formed in nuclear collisions at the LHC. Within a kinetic-rate equation approach as previously used for charmonia, the formation and dissociation of the $X (3872)$ is controlled by two transport parameters, i.e., its inelastic reaction rate and thermal-equilibrium limit in the evolving hot QCD medium. While the equilibrium limit is controlled by the charm production cross section in primordial nucleon-nucleon collisions (together with the spectra of charm states in the medium), the structure information is encoded in the reaction rate. We study how different scenarios for the rate affect the centrality dependence and transverse-momentum ( $p_{T}$ ) spectra of the $X (3872)$ . Larger reaction rates associated with the loosely bound molecule structure imply that it is formed later in the fireball evolution than the tetraquark and thus its final yields are generally smaller by around a factor of two, which is qualitatively different from most coalescence model calculations to date. The $p_{T}$ spectra provide further information as the later decoupling time within the molecular scenario leads to harder spectra caused by the blue-shift from the expanding fireball.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
2006.09945 [pdf]
EPJA(2021)·75 citations
06
[Submitted on 16 Jun 2020] (cross-list from hep-ph)
Hydrodynamic attractor of a hybrid viscous fluid in Bjorken flow
Toshali Mitra🇮🇳 · Sukrut Mondkar🇮🇳 · Ayan Mukhopadhyay🇮🇳 · Anton Rebhan🇦🇹 · Alexander Soloviev🇺🇸
The nonequilibrium evolution in a boost-invariant Bjorken flow of a hybrid viscous fluid model containing two interacting components with different viscosities, such that they represent strongly and weakly self-coupled sectors, is shown to be characterized by a hydrodynamic attractor which has an early-time behavior that is reminiscent of the so-called bottom-up thermalization scenario in heavy-ion collisions. The hydrodynamization times for the two sectors can differ strongly, with details depending on the curve realized on the two-dimensional attractor surface, which might account for different scenarios for small and large systems in nuclear collisions. The total system behaves like a single viscous fluid with a dynamically determined effective shear viscosity.
Comments:
7 pages, 3 figures, 1 table; v2: minor corrections and some extensions
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.09383 [pdf]
PRResearch(2020)·24 citations
07
[Submitted on 16 Jun 2020] (cross-list from hep-ph)
Nonrelativistic model of tetraquarks and predictions for their masses from fits to charmed and bottom meson data
Per Lundhammar🇸🇪 · Tommy Ohlsson🇸🇪
We investigate a nonrelativistic model of tetraquarks, which are assumed to be compact and to consist of diquark-antidiquark pairs. We fit, for the first time, basically all currently known values for the measured masses of 45 mesons, including both charmed and bottom mesons, to the model and predict masses of tetraquarks as well as diquarks. In particular, we find masses of four axial-vector diquarks, i.e., $q c$ , $cc$ , $q b$ , and $bb$ , where $q = u, d$ , and 24 ground-state tetraquarks, including both heavy-light tetraquarks ( $q c q c$ and $q b q b$ ) and heavy tetraquarks ( $cc cc$ and $bb bb$ ). In general, our results for the masses of $q b q b$ , $cc cc$ , and $bb bb$ are largely comparable with other reported results, whereas our results for the masses of $q c q c$ are slightly larger than what has been found earlier. Finally, we identify some of the obtained predictions for masses of tetraquarks with masses of experimental tetraquark candidates, and especially, we find that $ψ (4660)$ , $Z_{b} (10610)$ , and $Z_{b} (10650)$ could be described by the model.
Comments:
12 pages, 1 figure. Final version published in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2006.09393 [pdf]
PRD(2020)·71 citations
08
[Submitted on 17 Jun 2020] (cross-list from cond-mat.quant-gas)
Fractional quantum Hall physics and higher-order momentum correlations in a few spinful fermionic contact-interacting ultracold atoms in rotating traps
Constantine Yannouleas · Uzi Landman
The fractional quantum Hall effect (FQHE) is theoretically investigated, with numerical and algebraic approaches, in assemblies of a few spinful ultracold neutral fermionic atoms, interacting via repulsive contact potentials and confined in a single rapidly rotating two-dimensional harmonic trap. Going beyond the commonly used second-order correlations in the real configuration space, the methodology in this paper will assist the analysis of experimental observations by providing benchmark results for $N$ -body spin-unresolved, as well as spin-resolved, momentum correlations measurable in time-of-flight experiments with individual particle detection. Our analysis shows that the few-body lowest-Landau-level (LLL) states with good magic angular momenta exhibit inherent ordered quantum structures in the $N$ -body correlations, similar to those associated with rotating Wigner molecules (WMs), familiar from the field of semiconductor quantum dots under high magnetic fields. The application of a small perturbing stirring potential induces, at the ensuing avoided crossings, formation of symmetry broken states exhibiting ordered polygonal-ring structures, explicitly manifest in the single-particle density profile of the trapped particles. Away from the crossings, an LLL state obtained from exact diagonalization of the microscopic Hamiltonian, found to be well-described by a (1,1,1) Halperin two-component variational wavefunction, represents also a spinful rotating WM. Analysis of the calculated LLL wavefunction enables a two-dimensional generalization of the Girardeau one-dimensional 'fermionization' scheme, originally invoked for mapping of bosonic-type wave functions to those of spinless fermions.
Comments:
33 pages with 12 color figures (includes Supplemental Material and MATHEMATICA scripts). Extensive clarifications and additions. Accepted for publication in Physical Review A. For related papers, see https://sites.gatech.edu/cyannouleas
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2006.09602 [pdf]
PRA(2020)·4 citations
09
[Submitted on 17 Jun 2020] (cross-list from hep-ph)
Quantum nucleation of up-down quark matter and astrophysical implications
Jing Ren🇨🇳 · Chen Zhang🇨🇦
Quark matter with only $u$ and $d$ quarks ( $u d$ QM) might be the ground state of baryonic matter at large baryon number $A > A_{min}$ . With $A_{min} ≳ 300$ , this has no direct conflict with the stability of ordinary nuclei. An intriguing test of this scenario is to look for quantum nucleation of $u d$ QM inside neutron stars due to their large baryon densities. In this paper, we study the transition rate of cold neutron stars to $u d$ quark stars ( $u d$ QSs) and the astrophysical implications, considering the relevant theoretical uncertainties and observational constraints. It turns out that a large portion of parameter space predicts an instantaneous transition, and so the observed neutron stars are mostly $u d$ QSs. We find this possibility still viable under the recent gravitational wave and pulsar observations, although there are debates on its compatibility with some observations that involve complicated structure of quark matter. The tension could be partially relieved in the two-families scenario, where the high-mass stars ( $M ≳ 2 M_{⊙}$ ) are all $u d$ QSs and the low-mass ones ( $M \sim 1.4 M_{⊙}$ ) are mostly hadronic stars. In this case, the slow transition of the low-mass hadronic stars points to a very specific class of hadronic models with moderately stiff EOSs, and $u d$ QM properties are also strongly constrained.
Comments:
26 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2006.09604 [pdf]
PRD(2020)·34 citations
10
[Submitted on 17 Jun 2020] (cross-list from physics.atom-ph)
Substantially enhanced deuteron-triton fusion probabilities in intense low-frequency laser fields
Xu Wang🇨🇳
Deuteron-triton (DT) fusion is the primary fusion reaction used in controlled fusion research, mainly for its relatively high reaction cross sections compared to other fusion options. Even so, to attain appreciable reaction probabilities very high temperatures (on the order of 10-100 million kelvins) are required, which are extremely challenging to achieve and maintain. We show that intense low-frequency laser fields, such as those in the near-infrared regime for the majority of intense laser facilities around the world, are highly effective in transferring energy to the DT system and enhancing the DT fusion probabilities. The fusion probabilities are shown to be enhanced by at least an order of magnitude in 800-nm laser fields with intensities on the order of 10 $^{21}$ W/cm $^{2}$ . The demanding temperature requirement of controlled nuclear fusion may be relaxed if intense low-frequency lasers are exploited.
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
arXiv:
2006.09634 [pdf]
PRC(2020)·24 citations
11
[Submitted on 17 Jun 2020] (cross-list from cond-mat.quant-gas)
From few to many bosons inside the unitary window: a transition between universal to non-universal behavior
A. Kievsky🇮🇹 · A. Polls🇪🇸 · B. Juliá-Díaz🇪🇸 · N. K. Timofeyuk🇬🇧 · M. Gattobigio🇫🇷
Universal behaviour in few-bosons systems close to the unitary limit, where two bosons become unbound, has been intensively investigated in recent years both experimentally and theoretically. In this particular region, called the unitary window, details of the inter-particle interactions are not important and observables, such as binding energies, can be characterized by a few parameters. With an increasing number of particles the short-range repulsion, present in all atomic, molecular or nuclear interactions, gradually induces deviations from the universal behaviour. In the present letter we discuss for the first time a simple way of incorporating non-universal behaviour through one specific parameter which controls the smooth transition of the system from universal to non-universal regime. Using a system of $N$ helium atoms as an example we calculate their ground state energies as trajectories within the unitary window and also show that the control parameters can be used to determine the energy per particle in homogeneous systems when $N \to \infty$ .
Comments:
6 pages, 3 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2006.09758 [pdf]
PRA(2020)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE