Nuclear Theory·nucl-th

Tuesday·August 18, 2020

14 papers—8 primary·6 cross-listed

01
Discovery vs. Precision in Nuclear Physics- A Tale of Three Scales
Gerald A. Miller🇺🇸
At least three length scales are important in gaining a complete understanding of the physics of nuclei. These are the radius of the nucleus, the average inter-nucleon separation distance, and the size of the nucleon. The connections between the different scales are examined by using examples that demonstrate the direct connection between short-distance and high momentum transfer physics and also that significant high momentum content of wave functions is inevitable. The nuclear size is connected via the independent-pair approximation to the nucleon-nucleon separation distance, and this distance is connected via the concept of virtuality to the EMC effect. An explanation of the latter is presented in terms of light-front holographic wave functions of QCD. The net result is that the three scales are closely related, so that a narrow focus on any given specific range of scales may prevent an understanding of the fundamental origins of nuclear properties. It is also determined that, under certain suitable conditions, experiments are able to measure the momentum dependence of wave functions.
nucl-thhep-phnucl-exPRC(2020)·9 citations
02
Ab initio neutrinoless double-beta decay matrix elements for 48Ca, 76Ge, and 82Se
A. Belley🇨🇦 · C. G. Payne🇨🇦 · S. R. Stroberg🇺🇸 · T. Miyagi🇨🇦 · J. D. Holt🇨🇦
We calculate basis-space converged neutrinoless $β β$ decay nuclear matrix elements for the lightest candidates: 48Ca, 76Ge and 82Se. Starting from initial two- and three-nucleon forces, we apply the ab initio in-medium similarity renormalization group to construct valence-space Hamiltonians and consistently transformed $β β$ -decay operators. We find that the tensor component is non-negligible in 76Ge and 82Se, and resulting nuclear matrix elements are overall 25-45% smaller than those obtained from the phenomenological shell model. While a final matrix element with uncertainties still requires substantial developments, this work nevertheless opens a path toward a true first-principles calculation of neutrinoless $β β$ decay in all nuclei relevant for ongoing large-scale searches.
nucl-thhep-phnucl-exPRL(2021)·134 citations
03
Improvements to the macroscopic-microscopic approach of nuclear fission
Marc Verriere · Matthew R. Mumpower
The well established macroscopic-microscopic (mac-mic) description of nuclear fission enables the prediction of fission fragment yields for a broad range of fissioning systems. In this work, we present several key enhancements to this approach. We improve upon the microscopic sector of nuclear potential energy surfaces by magnifying the resolution of the Lipkin-Nogami equations and strengthening the Strutinsky procedure, thus reducing spurious effects from the continuum. We further present a novel deterministic method for calculating fission dynamics under the assumption of strongly damped nucleonic motion. Our technique directly determines the evolution of the scissioned shape distribution according to the number of random walk steps rather than the statistical accumulation of fission events. We show that our new technique is equivalent to the Metropolis random walk pioneered over the past decade by Randrup and colleagues. It further improves upon it, as we remove the need for altering the nuclear landscape via a biased potential. With our final improvement, we calculate fission fragments mass and charge distributions using particle number projection, which affords the simultaneous calculation of both mass and charge yield distributions. Fission fragments are thus calculated from the quantum mechanical $A$ -body states of the potential energy surface rather than the collective mass asymmetry variable ( $α_{g}$ ) of the Finite-Range Liquid-Drop Model (FRLDM) used in past work. We highlight the success of our enhancements by predicting the odd-even staggering and the charge polarization for the neutron-induced fission of $^{233}$ U and $^{235}$ U.
nucl-thPRC(2021)·21 citations
04
Role of $Δ$ s in determining the properties of Neutron Stars in parameterized hydrostatic equilibrium
Debashree Sen🇮🇳
The possible existence of $Δ$ resonances is inspected in the cold dense matter of neutron star (NS) core in presence of the hyperons. The diverse effects of variation in $Δ$ mass on their formation and the equation of state (EoS) are studied in this work with an effective chiral model and the resultant NS properties are calculated with the help of parameterized Tolman-Oppenheimer-Volkoff equations (PTOV) to bring out the two important features of pressure in the context of massive NSs. The $Δ$ puzzle is re-explored and resolved taking into account the concept of modified/parameterized inertial pressure and self-gravity in case of massive pulsars like PSR J1614-2230 and PSR J0348-0432. It is seen that although the presence of exotic matter like the hyperons and the $Δ$ s softens the EoS considerably, their presence in massive NSs can be successfully explained with the theory of parameterized hydrostatic equilibrium conditions. The results of this work also satisfy the constraints on $R_{1.4}$ and $R_{1.6}$ from the gravitational wave (GW170817) detection of binary NS merger. The constraint on baryonic mass from PSR J0737-3039 is also satisfied with the solutions of the PTOV equations for all the $Δ$ masses considered.
nucl-thInt.J.Mod.Phys.D(2019)·7 citations
05
Binding of antikaons and Lambda(1405) clusters in light kaonic nuclei
Yoshiko Kanada-En'yo🇯🇵
The energy spectra of light-mass kaonic nuclei were investigated using the theoretical framework of the $0 s$ -orbital model with zero-range $K ˉ N$ and $K ˉ K ˉ$ interactions of effective single-channel real potentials. The energies of the $K ˉ N N$ , $K ˉ N N N$ , $K ˉ N N N N$ , $K ˉ K ˉ N$ , and $K ˉ K ˉ N N$ systems were calculated in the cases of weak- and deep-binding of the $K ˉ N$ interaction, which was adjusted to fit the $Λ (1405)$ mass with the energy of the $K ˉ N$ bound state. The results qualitatively reproduced the energy systematics of kaonic nuclei calculated via other theoretical approaches. In the energy spectra of the $K ˉ N N$ and $K ˉ K ˉ N N$ systems, the lowest states $K ˉ N N (J^{π}, T = 0^{-}, 1/2)$ and $K ˉ K ˉ N N (0^{+}, 0)$ were found to have binding energies approximately twice and four times as large as that of the $K ˉ N (1/ 2^{-}, 0)$ state, respectively. Higher $(J^{π}, T)$ states including $K ˉ N N (1^{-}, 1/2)$ , $K ˉ K ˉ N N (0^{+}, 1)$ , and $K ˉ K ˉ N N (1^{+}, 1)$ were predicted at energies of 9--25 MeV below the antikaon-decay threshold. The effective $Λ (1405)$ - $Λ (1405)$ interaction in the $K ˉ K ˉ N N$ system was also investigated via a $K ˉ N + K ˉ N$ -cluster model. Strong and weak $Λ (1405)$ - $Λ (1405)$ attractions were obtained in the $S^{π} = 0^{+}$ and $S^{π} = 1^{-}$ channels, respectively. The $Λ (1405)$ - $Λ (1405)$ interaction in the $ $K ˉ K ˉ N N$ system was compared with the effective $d$ - $d$ interaction in the $N N N N$ system, and the properties of dimer-dimer interactions in hadron and nuclear systems were discussed.
nucl-thEPJA(2021)·6 citations
06
A bag model of matter condensed by the strong interaction
Zhi-Qiang Miao🇨🇳 · Cheng-Jun Xia🇨🇳 · Xiao-Yu Lai🇨🇳 · Toshiki Maruyama🇯🇵 · Ren-Xin Xu🇨🇳 · En-Ping Zhou🇩🇪
Inspired by various astrophysical phenomenons, it is suggested that pulsar-like compact stars are comprised entirely of strangeons (quark-clusters with three-light-flavor symmetry) and a small amount of electrons. In order to better constrain the properties of strangeon stars, we propose a linked bag model to describe the condensed matter by the strong interaction (i.e., strong condensed matter) in both 2-flavoured (nucleons) and 3-flavoured (hyperons, strangeons, etc.) scenarios. The model parameters are calibrated to reproduce the saturation properties of nuclear matter, which are later applied to hyperon matter and strangeon matter. Compared with baryon matter, the derived energy per baryon of strangeon matter is reduced if the strangeon carries a large number of valence quarks, which stiffens the equation of state and consequently increases the maximum mass of strangeon stars. In a large parameter space, the maximum mass and tidal deformability of strangeon stars predicted by the linked bag model are consistent with the current astrophysical constraints. It is found that the maximum mass of strangeon stars can be as large as $\sim 2.5 M_{⊙}$ , while the tidal deformability of a $1.4 M_{⊙}$ strangeon star lies in the range of $180 ≲ Λ_{1.4} ≲ 340$ .
nucl-thastro-ph.HEIJMPE(2022)·25 citations
07
Dibaryons: Molecular versus Compact Hexaquarks
H. Clement🇩🇪 · T. Skorodko🇩🇪
Hexaquarks constitute a natural extension of complex quark systems like also tetra- and pentaquarks do. To this end the current status of $d^{*} (2380)$ in both experiment and theory is shortly reviewed. Recent high-precision measurements in the nucleon-nucleon channel and analyses thereof have established $d^{*} (2380)$ as an indisputable resonance in the long-sought dibaryon channel. Important features of this $I (J^{P}) = 0 (3^{+})$ state are its narrow width and its deep binding relative to the $Δ (1232) Δ (1232)$ threshold. Its decay branchings favor theoretical calculations predicting a compact hexaquark nature of this state. We review the current status of experimental and theoretical studies on $d^{*} (2380)$ as well as new physics aspects it may bring in the future. In addition, we review the situation at the $Δ (1232) N$ and $N^{*} (1440) N$ thresholds, where evidence for a number of resonances of presumably molecular nature have been found -- similar to the situation in charmed and beauty sectors. Finally we briefly discuss the situation of dibaryon searches in the flavored quark sectors.
nucl-thhep-exhep-phnucl-exCPC(2021)·28 citations
08
Collective nuclear vibrations and initial state shape fluctuations in central Pb+Pb collisions: resolving the $v_{2}$ to $v_{3}$ puzzle
B.G. Zakharov🇷🇺
We have studied, for the first time, the influence of the collective quantum effects in the nuclear wave functions on the azimuthal anisotropy coefficients $ϵ_{2, 3}$ in the central Pb+Pb collisions at the LHC energies. With the help of the energy weighted sum rule we demonstrate that the classical treatment with the Woods-Saxon nuclear density overestimates the mean square quadrupole moment of the $^{208}$ Pb nucleus by a factor of $\sim 2.2$ . The Monte-Carlo Glauber simulation of the central Pb+Pb collisions accounting for the restriction on the quadrupole moment leads to $ϵ_{2} / ϵ_{3} \approx 0.8$ which allows to resolve the $v_{2}$ -to- $v_{3}$ puzzle.
nucl-thhep-phJETP Lett.(2020)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE