Nuclear Theory·nucl-th

Tuesday·May 24, 2022

11 papers—5 primary·6 cross-listed

01
Magnetic dipole moments as a strong signature for $α$ -clustering in even-even self-conjugate nuclei
Gianluca Stellin · Karl-Heinz Speidel · Ulf-G. Meißner
We investigate the magnetic dipole moments in even-even self-conjugate nuclei from $^{12} C$ to $^{44} Ti$ . For the latter, the measured gyromagnetic factors of excited states turn out to assume the same value of $g \approx + 0.5$ within statistical errors. This peculiar feature can be interpreted on the basis of collective excitations of $α$ -clusters. Analogously, the behaviour of the same observable is studied for all isotopes obtained by adding one or two neutrons to the considered self-conjugate nuclei. It is found that for the $N = Z + 1$ isotopes the $α$ -cluster structure hardly contributes to the observed negative g- factor value, corroborating molecular $α$ -cluster models. The addition of a further neutron, however, restores the original $α$ -cluster g-factors, except for the semi-magic isotopes, in which the deviations from $g \approx + 0.5$ can be associated with the relevant shell closures. Secondly, we analyze the same observable in the framework of a macroscopic $α$ -cluster model on a finite lattice of side length $L$ . We focus on the discretization effects induced in the magnetic dipole moments of the $2_{1}^{+}$ and the $3_{1}^{-}$ states of $^{12} C$ at different values of the lattice spacing $a$ .
nucl-thEPJA(2022)·5 citations
02
Effects of pairing gap and band gap on superfluid density in the inner crust of neutron stars
Yuki Minami · Gentaro Watanabe
Calculations of the superfluid density in the inner crust of neutron stars by different approaches are in strong disagreement, which causes a debate on the accountability of pulsar glitches based on superfluidity. Taking a simple unified model, we study the dependence on approximation of the superfluid density in a periodic potential. In comparison with the Hartree-Fock-Bogoliubov (HF-Bogoliubov) theory which treats the effects of the band gap and the pairing gap on equal footing, we examine the HF-BCS-type approximation in which the former is incorporated in priority, and another approximation in which the latter is incorporated in priority. We find that, when the pairing gap and the band gap are comparable as in the inner crust of neutron stars, they need to be treated on equal footing, and the HF-BCS approximation can considerably underestimate the superfluid density even if the pairing gap is much smaller than the Fermi energy. Our result suggests that the validity of the HF-BCS approximation for evaluating the superfluid density in neutron star crusts is questionable.
nucl-thastro-ph.HEcond-mat.quant-gasPRResearch(2022)·15 citations
03
Spinodal Enhancement of Light Nuclei Yield Ratio in Relativistic Heavy Ion Collisions
Kai-Jia Sun🇺🇸 · Wen-Hao Zhou🇨🇳 · Lie-Wen Chen🇨🇳 · Che Ming Ko🇺🇸 · Feng Li🇨🇳 · Rui Wang🇨🇳 · Jun Xu🇨🇳
Using a relativistic transport model to describe the evolution of the quantum chromodynamic matter produced in Au+Au collisions at $s_{N N} = 3 - 200$ GeV, we study the effect of a first-order phase transition in the equation of state of this matter on the yield ratio $N_{t} N_{p} / N_{d}^{2}$ ( $tp / d^{2}$ ) of produced proton ( $p$ ), deuteron ( $d$ ), and triton ( $t$ ). We find that the large density inhomogeneities generated by the spinodal instability during the first-order phase transition can survive the fast expansion of the subsequent hadronic matter and lead to an enhanced $tp / d^{2}$ in central collisions at $s_{N N} = 3 - 5$ GeV as seen in the experiments by the STAR Collaboration and the E864 Collaboration. However, this enhancement subsides with increasing collision centrality, and the resulting almost flat centrality dependence of $tp / d^{2}$ at $s_{N N} = 3$ GeV can also be used as a signal for the first-order phase transition.
nucl-thhep-ph13 citations
04
Modeling Neutron Star Matter in the Age of Multimessenger Astrophysics
Omar Benhar · Alessandro Lovato · Giovanni Camelio
The interpretation of the available and forthcoming data obtained from multimessenger astrophysical observations -- potentially providing unprecedented access to neutron star properties -- will require the development of novel, accurate theoretical models of dense matter. Of great importance, in this context, will be the capability to devise a description of thermal effects applicable to the study of quantities other than the equation of state, such as the transport coefficients and the neutrino mean free path in the nuclear medium. The formalism based on correlated basis states and the cluster expansion technique has been previously employed to derive a well-behaved effective interaction -- suitable for use in standard perturbation theory -- from a state-of-the-art nuclear Hamiltonian, including phenomenological two- and three-nucleon potentials. Here, we provide a comprehensive and self-contained account of the extension of this approach to the treatment of finite-temperature effects, and report the results of numerical calculations of a number of properties of nuclear matter with arbitrary neutron excess and temperature up to 50 MeV.
nucl-thApJ(2022)·8 citations
05
Systematic shell model study for $N = 82$ and $N = 126$ isotones and nuclear isomers
Bharti Bhoy · Praveen C. Srivastava
In the present work, we have done a systematic shell model study of $N = 82$ and $N = 126$ isotones. For the $N = 82$ isotones, we have performed calculations using SN100PN interaction, while for $N = 126$ isotones, we have used KHPE interaction. Similarities between these two isotonic chains have been reported, using the strong resemblance between the high- $j$ orbitals. Apart from the nuclear spectroscopic properties, we have also explained different isomeric states in these two regions. In the $N$ =82 region, we have mainly discussed the properties of the $6^{+}$ and $17/ 2^{+}$ isomers, while in the $N = 126$ region for $8^{+}$ , $1 1^{-}$ , $21/ 2^{-}$ and $29/ 2^{+}$ isomers. We have reported $B (E 2)$ , $B (E 3)$ , $g$ -factor, and quadrupole moments of the isomeric states for comparison in these two isotonic chains.
nucl-thnucl-exJ.Phys.G(2022)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE

Magnetic dipole moments as a strong signature for α-clustering in even-even self-conjugate nuclei

Effects of pairing gap and band gap on superfluid density in the inner crust of neutron stars

Spinodal Enhancement of Light Nuclei Yield Ratio in Relativistic Heavy Ion Collisions

Modeling Neutron Star Matter in the Age of Multimessenger Astrophysics

Systematic shell model study for N=82 and N=126 isotones and nuclear isomers

Affiliations

Magnetic dipole moments as a strong signature for $α$ -clustering in even-even self-conjugate nuclei

Systematic shell model study for $N = 82$ and $N = 126$ isotones and nuclear isomers