Nuclear Theory·nucl-th

Wednesday·July 1, 2020

14 papers—8 primary·6 cross-listed

01
The outer crust of a cold, non-accreting neutron star within the Quark-Meson Coupling (QMC) model
Sofija Antić🇦🇺 · Jirina R. Stone🇺🇸 · John C. Miller🇬🇧 · Kay Marie L. Martinez🇦🇺 · Anthony William Thomas🇦🇺 · Pierre A. M. Guichon🇫🇷
The outer crust properties of cold non-accreting neutron stars are studied within the framework of the quark-meson coupling (QMC) model, which includes the effects of modifications of the quark structure inside individual nucleons when they are within a high-density nuclear medium. With a unique set of five well-constrained adjustable parameters, which have a clear physical basis, the QMC model gives predictions for the ground state observables of even-even nuclei which agree with experiment as well as traditional models. Furthermore, it gives improved theoretical values for nuclei thought to play a role in the outer crusts of neutron stars but for which experimental data is not available. Using the latest experimental data tables wherever possible but otherwise the predictions from the QMC model, we construct an equation of state for the outer crust which is then used within stellar model calculations to obtain an equilibrium sequence of crustal layers, each characterized by a particular neutron rich nuclei. Various properties of the layers are calculated for a range of neutron-star masses, and comparisons are made with alternative equations of state from the literature. This leads to the conclusion that the QMC model successfully predicts the outer crust properties and is fully comparable with the more traditional mass models, which all depend on a larger number of parameters.
nucl-thastro-ph.HEPRC(2020)·9 citations
02
$ΛΛ N$ - $Ξ N N$ $S$ wave resonance
H. Garcilazo · A. Valcarce
We use an existing model of the $ΛΛ N - Ξ N N$ three-body system based in two-body separable interactions to study the $(I, J^{P}) = (1/2, 1/ 2^{+})$ three-body channel. For the $ΛΛ$ , $Ξ N$ , and $ΛΛ - Ξ N$ amplitudes we have constructed separable potentials based on the most recent results of the HAL QCD Collaboration. They are characterized by the existence of a resonance just below or above the $Ξ N$ threshold in the so-called $H$ -dibaryon channel, $(i, j^{p}) = (0, 0^{+})$ . A three-body resonance appears {2.3} MeV above the $Ξ d$ threshold. We show that if the $ΛΛ - Ξ N$ $H$ -dibaryon channel is not considered, the $ΛΛ N - Ξ N N$ $S$ wave resonance disappears. Thus, the possible existence of a $ΛΛ N - Ξ N N$ resonance would be sensitive to the $ΛΛ - Ξ N$ interaction. The existence or nonexistence of this resonance could be evidenced by measuring, for example, the $Ξ d$ cross section.
nucl-thhep-phCPC(2020)·6 citations
03
Shape phase transitions in odd-A Zr isotopes
K. Nomura · T. Nikšić · D. Vretenar
Spectroscopic properties that characterize shape phase transitions in neutron-rich odd-A Zr isotopes are investigated using the framework of nuclear density functional theory and particle-core coupling. The interacting-boson Hamiltonian of the even-even core nuclei, and the single-particle energies and occupation probabilities of the unpaired neutron are completely determined by deformation constrained self-consistent mean-field calculations based on the relativistic Hartree-Bogoliubov model with a choice of a universal energy density functional and pairing interaction. The triaxial $(β, γ)$ deformation energy surfaces for even-even $^{94 - 102}$ Zr indicates transition from triaxial or $γ$ -soft ( $^{94, 96}$ Zr) to prolate ( $^{98}$ Zr), and triaxial ( $^{100, 102}$ Zr) shapes. The corresponding low-energy excitation spectra of the odd-A Zr isotopes are in very good agreement with recent experimental results. Consistent with the structural evolution of the neighboring even-even Zr nuclei, the state-dependent effective deformations and their fluctuations in the odd-A isotopes indicate a pronounced discontinuity around the transitional nucleus $^{99}$ Zr.
nucl-thnucl-exPRC(2020)·17 citations
04
Femtoscopy scales and particle production in the relativistic heavy ion collisions from Au+Au at 200 AGeV to Xe+Xe at 5.44 ATeV within the integrated hydrokinetic model
V. M. Shapoval🇺🇦 · M. D. Adzhymambetov🇺🇦 · Yu. M. Sinyukov🇺🇦
The recent results on the main soft observables, including hadron and photon yields and particle number ratios, $p_{T}$ spectra, flow harmonics, as well as the femtoscopy radii, obtained within the integrated hydrokinetic model (iHKM) for high-energy heavy-ion collisions are reviewed and re-examined. The cases of different nuclei colliding at different energies are considered: Au+Au collisions at the top RHIC energy $s_{N N} = 200$ GeV, Pb+Pb collisions at the LHC energies $s_{N N} = 2.76$ TeV and $s_{N N} = 5.02$ TeV, and the LHC Xe+Xe collisions at $s_{N N} = 5.44$ TeV. The effect of the initial conditions and the model parameters, including the utilized equation of state (EoS) for quark-gluon phase, on the simulation results, as well as the role of the final afterburner stage of the matter evolution are discussed. The possible solution of the so-called ``photon puzzle'' is considered. The attention is also paid to the dependency of the interferometry volume and individual interferometry radii on the initial transverse geometrical size of the system formed in the collision.
nucl-thhep-phEPJA(2020)·11 citations
05
Revisiting the hypertriton lifetime puzzle
A. Pérez-Obiol🇯🇵 · D. Gazda🇨🇿 · E. Friedman🇮🇱 · A. Gal🇮🇱
Conflicting values of the hypertriton ( $_{Λ}^{3}$ H) lifetime were extracted in recent relativistic heavy-ion collision experiments. The ALICE Collaboration's reported $_{Λ}^{3}$ H lifetime $τ (_{Λ}^{3}$ H) is compatible within measurement uncertainties with the free $Λ$ lifetime $τ_{Λ}$ , as naively expected for a loosely bound $Λ$ hyperon in $_{Λ}^{3}$ H, whereas STAR's reported range of $τ (_{Λ}^{3}$ H) values is considerably shorter: $τ_{STAR} (_{Λ}^{3}$ H) $\sim$ (0.4-0.7) $τ_{Λ}$ . This $_{Λ}^{3}$ H lifetime puzzle is revisited theoretically using $_{Λ}^{3}$ H three-body wavefunctions generated in a chiral effective field theory approach to calculate the decay rate $Γ (_{Λ}^{3}$ H $\to^{3}$ He $+ π^{-}$ ). Significant but opposing contributions arise from $Σ N N$ admixtures in $_{Λ}^{3}$ H and from $π^{-}$ - $^{3}$ He final-state interaction. Evaluating the inclusive $π^{-}$ decay rate $Γ_{π^{-}} (_{Λ}^{3}$ H) via a branching ratio $Γ (_{Λ}^{3}$ H $\to^{3}$ He+ $π^{-}) / Γ_{π^{-}} (_{Λ}^{3}$ H) determined in helium bubble-chamber experiments, and adding $Γ_{π^{0}} (_{Λ}^{3}$ H) through the $Δ I = \frac{1}{2}$ rule, we derive $τ (_{Λ}^{3}$ H) assuming several different values of the $Λ$ separation energy $B_{Λ} (_{Λ}^{3}$ H). It is concluded that each of ALICE and STAR reported $τ (_{Λ}^{3}$ H) intervals implies its own constraint on $B_{Λ} (_{Λ}^{3}$ H): $B_{Λ} ≲ 0.1$ MeV for ALICE, $B_{Λ} ≳ 0.2$ MeV for STAR.
nucl-thhep-phnucl-exPLB(2020)·28 citations
06
Description of alpha-clustering of 8Be nucleus states in high-precision theoretical approach
D. M. Rodkin · Yu. M. Tchuvil'sky
Scrupulous theoretical study of 8Be nucleus states, both clustered and non-clustered, is performed over a wide range of the excitation energies. The quantities which characterize the degree of the alpha-clustering of these states: spectroscopic factors, cluster form factors as well as the alpha-decay widths are computed in the framework of an accurate ab initio approach developed. Other basic properties of 8Be spectrum: the binding and excitation energies, mean values of the isospin are calculated simultaneously. In the majority of instances the results of the computations turn out to be in a good agreement with the spectroscopic data. A number of predictions are made and corresponding verification experiment is proposed. Prospects of the developed approach for nuclear spectroscopy are demonstrated.
nucl-thCPC(2020)·10 citations
07
Accurate bulk properties of nuclei from $A = 2$ to $\infty$ from potentials with $Δ$ isobars
W.G. Jiang🇺🇸 · A. Ekström🇸🇪 · C. Forssén🇸🇪 · G. Hagen🇺🇸 · G.R. Jansen🇺🇸 · T. Papenbrock🇺🇸
We optimize $Δ$ -full nuclear interactions from chiral effective field theory. The low-energy constants of the contact potentials are constrained by two-body scattering phase shifts, and by properties of bound-state of $A = 2$ to $4$ nucleon systems and nuclear matter. The pion-nucleon couplings are taken from a Roy-Steiner analysis. The resulting interactions yield accurate binding energies and radii for a range of nuclei from $A = 16$ to $A = 132$ , and provide accurate equations of state for nuclear matter and realistic symmetry energies. Selected excited states are also in agreement with data.
nucl-thPRC(2020)·215 citations
08
Merging of transport theory with TDHF: multinucleon transfer in U+U collisions
S. Ayik · B. Yilmaz · O. Yilmaz · A.S. Umar
Multinucleon transfer mechanism in the collision of $^{238} U +^{238} U$ system is investigated at $E_{c.m.} = 833$ MeV in the framework of the quantal diffusion description based on the stochastic mean-field approach (SMF). Double cross-sections $σ (N, Z)$ as a function of the neutron and proton numbers, the cross-sections $σ (Z)$ and $σ (A)$ as a function of the atomic numbers and the mass numbers are calculated for production of the primary fragments. The calculation indicates the $^{238} U +^{238} U$ system may be located at an unstable equilibrium state at the potential energy surface with a slightly negative curvature along the beta stability line on the $(N, Z) -$ plane. This behavior may lead to rather large diffusion along the beta stability direction.
nucl-thPRC(2020)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE