Nuclear Theory·nucl-th

Wednesday·October 14, 2020

8 papers—7 primary·1 cross-listed

01
Surface and curvature properties of charged strangelets in compact objects
G. Lugones🇧🇷 · A. G. Grunfeld🇦🇷
Droplets of absolutely stable strange quark matter (strangelets) immersed in a lepton background may be the energetically preferred composition of strange star crusts and of the interior of a new class of stars known as strangelet dwarfs. In this work we calculate the surface tension $σ$ and the curvature coefficient $γ$ of charged strangelets as a function of the baryon number density, the temperature, the chemical potential of trapped neutrinos, the strangelet size, the electric potential and the electric charge at their boundary. Strange quark matter in chemical equilibrium and with global electric charge neutrality is described within the MIT bag model. We focus on three different astrophysical scenarios, namely cold strange stars, proto strange stars and post merger strange stars. Finite size effects are implemented within the multiple reflection expansion framework. We find that $σ$ decreases significantly as the strangelet's boundary becomes more positively charged. This occurs because $σ$ is dominated by the contribution of $s$ quarks which are the most massive particles in the system. Negatively charged $s$ -quarks are suppressed in strangelets with a large positive electric charge, diminishing their contribution to $σ$ and resulting in smaller values of the total $σ$ . We verify that the more extreme astrophysical scenarios, with higher temperatures and higher neutrino chemical potentials, allow higher positive values of the strangelet's electric charge at the boundary and consequently smaller values of $σ$ . In contrast, $γ$ is strongly dominated by the density of light ( $u$ and $d$ ) quarks and is quite independent of the charge-per-baryon ratio, the temperature and neutrino trapping. We discuss the relative importance of surface and curvature effects as well as some astrophysical consequences of these results.
nucl-thastro-ph.HEhep-phhep-thPRC(2021)·19 citations
02
Quantum entanglement in nuclear Cooper pair tunneling with $γ$ -rays
G. Potel · F. Barranco · E. Vigezzi · R. A. Broglia
While Josephson-like junctions, transiently established in heavy ion collisions ( $τ_{co l l} \approx 1 0^{- 21}$ s) between superfluid nuclei --through which Cooper pair tunneling ( $Q$ -value $Q_{2 n}$ ) proceeds mainly in terms of successive transfer of entangled nucleons-- is deprived from the macroscopic aspects of a supercurrent, it displays many of the special effects associated with spontaneous symmetry breaking in gauge space (BCS condensation), which can be studied in terms of individual quantum states and of tunneling of single Cooper pairs. From the results of studies of one- and two- neutron transfer reactions carried out at energies below the Coulomb barrier we estimate the value of the mean square radius (correlation length) of the nuclear Cooper pair. A quantity related to the largest distance of closest approach for which the absolute two-nucleon tunneling cross section is of the order of the single-particle one. Furthermore, emission of $γ$ -rays of (Josephson) frequency $ν_{J} = Q_{2 n} / h$ distributed over an energy range $ℏ/ τ_{co l l}$ is predicted.
nucl-thnucl-exPRC(2021)·21 citations
03
Effective field theory analysis of boson-trimer bond lengths to next-to-leading order
Julia Qin · Jared Vanasse
Cold Helium atoms are a unique system where a single excited three-body Efimov state occurs, naturally, without the need for an external magnetic field. While three-body bound state energies of cold Helium atoms have previously been investigated, recent experimental techniques have allowed their structure to also be studied. The weak interaction between Helium atoms leads to a helium-helium (dimer) scattering length, $a$ , much larger than the helium-helium effective range of interaction, $r$ . This feature is exploited in a theory that systematically expands observables in powers of $r / a$ , known as short range effective field theory (srEFT), which has been used successfully to investigate properties of cold atom systems. Using srEFT we investigate the average bond length of atoms in the three-body ground state and excited Efimov state of cold Helium atoms. At leading-order (next-to-leading order) in srEFT, we find the average bond length of the $^{4}$ He trimer ground state is 8.35(33) Å (10.29(2) Å) and the average bond length of the excited $^{4}$ He trimer Efimov state is 103(4) Å (105.3(2) Å).
nucl-thphysics.atm-clusPRA(2021)·2 citations
04
Two-proton radioactivity of exotic nuclei beyond proton drip-line
Yanzhao Wang · Jianpo Cui · Yonghao Gao · Jianzhong Gu
To search for new candidates of the true and simultaneous two-proton ( $2 p$ ) radioactivity, the $2 p$ decay energies (\textit{Q} $_{2 p}$ ) are extracted by the Weizsäcker-Skyrme-4 (WS4) model, the finite-range droplet model (FRDM), the Kourra-Tachibaba-Uno-Yamada (KTUY) model and the Hartree-Fock-Bogoliubov mean-field model with the BSk29 Skyrme interaction (HFB29). Then, the $2 p$ radioactivity half-lives are calculated within the generalized liquid drop model (GLDM) by inputting the four types of \textit{Q} $_{2 p}$ values. By the energy and half-life constraints, it is found that the probable $2 p$ decay candidates are the nuclei beyond the proton-drip line in the region of \textit{Z} $<$ 50 or \textit{Z} $\leq 50$ based on each nuclear mass model. In the region beyond \textit{Z}=50, the $2 p$ -decaying candidates are predicted only using the HFB29 mass model. Finally, the competition between the true $2 p$ radioactivity and $α$ -decay for the nuclei above the \textit{N}=\textit{Z}=50 shell closures is discussed. It is shown that $^{101}$ Te, $^{111}$ Ba and $^{114}$ Ce prefer to $2 p$ radioactivity and the dominant decay mode of $^{107}$ Xe and $^{116}$ Ce is $α$ -decay.
nucl-thCommun.Theor.Phys.(2021)·21 citations
05
Mirror energy differences in T=1/2 f7/2-shell nuclei within isospin-dependent DFT
P. Baczyk · W. Satula
Background: Small asymmetry between neutrons and protons, caused by the differences in masses and charges of the up and down constituent quarks leads to the isospin symmetry breaking. The isospin non-conservation affects broad range of observables from superallowed Fermi weak interaction to isospin-forbidden electromagnetic rates. Its most profound and cleanest manifestation are systematic shifts in masses and excitation energies of mirror atomic nuclei. Purpose: Recently, we constructed the charge-dependent DFT that includes class II and III local interactions and demonstrated that the model allows for very accurate reproduction of Mirror and Triplet Displacement energies in a very broad range of masses. The aim of this work is to further test the charge-dependent functional by studying Mirror Energy Differences (MEDs) in function of angular momentum $I$ . Methods: To compute MEDs we use DFT-rooted no core configuration interaction model. This post mean-field method restores rotational symmetry and takes into account configuration mixing within a space that includes relevant (multi)particle-(multi)hole Slater determinants. Results: We applied the model to $f_{7/2}$ -shell mirror pairs of $A = 43$ , $45$ , $47$ , and $49$ focusing on MEDs in low-spin part (below band crossing) what allowed us to limit the model space to seniority one and three (one broken pair) configurations. Conclusions: We demonstrate that, for spins $I \leq 15/2$ being subject of the present study, our model reproduces well experimental MEDs which vary strongly in function of $I$ and $A$ . The quality of model's predictions is comparable to the nuclear shell-model results by Bentley et al. Phys. Rev. C 92, 024310 (2015).
nucl-thPRC(2021)·10 citations
06
Initialization effects of nucleon profile on the $π$ yields in heavy-ion collisions at medium energies
Zu-Xing Yang🇨🇳 · Nicolas Michel🇨🇳 · Xiao-Hua Fan🇨🇳 · Wei Zuo🇨🇳
We study a problem of $π$ production in heavy ion collisions in the context of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model. We generated nucleon densities using two different models, the Skyrme-Hartree-Fock (SHF) model and configuration interaction shell model (SM). Indeed, inter-nucleon correlations are explicitly taken into account in SM, while they are averaged in the SHF model. As an application of our theoretical frameworks, we calculated the $π^{-}$ and $π^{+}$ yields in collisions of nuclei with $A = 30 - 40$ nucleons. We used different harmonic oscillator lengths $b_{H O}$ to generate the harmonic oscillator basis for SM in order to study both theoretical and experimental cases. It is found that SM framework with $b_{H O}$ = 2.5 fm and SHF can be distinguished by the yield of $π$ mesons, in this case the density distribution calculated by the shell model produces more $π$ in the collision. In comparison, SM with $b_{H O}$ = 2.0 fm is characterized from SHF by the double $π^{-} / π^{+}$ ratios with different large impact parameters, from which one can find the double $π^{-} / π^{+}$ ratios of SM change smoother and are less than those of SHF.
nucl-thJ.Phys.G(2021)·8 citations
07
Evolution of $β$ -decay half-lives at finite-temperatures
A. Ravlic · E. Yuksel · Y. F. Niu · N. Paar
$β$ -decay properties of nuclei are investigated within the relativistic nuclear energy density functional framework by varying the temperature and density, conditions relevant to the final stages of stellar evolution. Both thermal and nuclear pairing effects are taken into account in the description of nuclear properties and in the finite temperature proton-neutron relativistic quasiparticle random-phase approximation (FT-PNRQRPA) to calculate the relevant allowed and first-forbidden transitions in the $β$ -decay. The temperature and density effects are studied on the $β$ -decay half-lives between temperatures $T = 0 - 1.5$ MeV, and at densities $ρ Y_{e} = 1 0^{7}$ g/cm $^{3}$ and $1 0^{9}$ g/cm $^{3}$ . The relevant Gamow-Teller transitions are also investigated for Ti, Fe, Cd, and Sn isotopic chains at finite temperatures. We find that the $β$ -decay half-lives increase with increasing density $ρ Y_{e}$ , whereas half-lives generally decrease with increasing temperature. It is shown that the temperature effects decrease the half-lives considerably in nuclei with longer half-lives at zero temperature, while only slight changes for nuclei with short half-lives are obtained. We also show the importance of including the de-excitation transitions in the calculation of the $β$ -decay half-lives at finite temperatures. Comparing the FT-PNQRPA results with the shell-model calculations for $p f -$ shell nuclei, a reasonable agreement is obtained for the temperature dependence of $β$ -decay rates. Finally, large-scale calculations of $β$ -decay half-lives are performed at temperatures $T_{9} (K) = 5$ and $T_{9} (K) = 10$ and densities $ρ Y_{e} = 1 0^{7}$ g/cm $^{3}$ and $1 0^{9}$ g/cm $^{3}$ for even-even nuclei in the range $8 \leq Z \leq 82$ , relevant for astrophysical nucleosynthesis mechanisms.
nucl-thastro-ph.SRnucl-ex3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Surface and curvature properties of charged strangelets in compact objects

Quantum entanglement in nuclear Cooper pair tunneling with γ-rays

Effective field theory analysis of boson-trimer bond lengths to next-to-leading order

Two-proton radioactivity of exotic nuclei beyond proton drip-line

Mirror energy differences in T=1/2 f7/2-shell nuclei within isospin-dependent DFT

Initialization effects of nucleon profile on the π yields in heavy-ion collisions at medium energies

Evolution of β-decay half-lives at finite-temperatures

Affiliations

Quantum entanglement in nuclear Cooper pair tunneling with $γ$ -rays

Initialization effects of nucleon profile on the $π$ yields in heavy-ion collisions at medium energies

Evolution of $β$ -decay half-lives at finite-temperatures