Nuclear Theory·nucl-th

Wednesday·April 5, 2023

13 papers—8 primary·5 cross-listed

01
Magnetic moments of $A = 3$ nuclei with chiral effective field theory operators
Soham Pal (1) · Shiplu Sarker (1) · Patrick J. Fasano (2) · Pieter Maris (1) · James P. Vary (1) · Mark A. Caprio (2) · Robert A. M. Basili (1) ((1) Iowa State University · (2) University of Notre-Dame)
Chiral effective field theory ( $χ$ EFT) provides a framework for obtaining internucleon interactions in a systematically improvable fashion from first principles, while also providing for the derivation of consistent electroweak current operators. In this work, we apply consistently derived interactions and currents towards calculating the magnetic dipole moments of the $A = 3$ systems Triton and Helium-3. We focus here on LENPIC interactions obtained using semilocal coordinate-space (SCS) regularization. Starting from the momentum-space representation of the LENPIC $χ$ EFT vector current, we derive the SCS-regularized magnetic dipole operator up through N2LO. We then carry out no-core shell model calculations for Triton and Helium-3 systems, using the SCS LENPIC interaction at N2LO in $χ$ EFT, and evaluate the magnetic dipole moments obtained using the consistently derived one-nucleon and two-nucleon electromagnetic currents. As anticipated by prior results with $χ$ EFT currents, the current corrections through N2LO provide improved, but not yet complete, agreement with experiment for the Triton and Helium-3 magnetic dipole moments.
nucl-thquant-phPRC(2023)·10 citations
02
Nuclear mass table in density functional approach inspired by neutron-star observations
Hana Gil · Nobuo Hinohara · Chang Ho Hyun · Kenichi Yoshida
Background: Nuclear energy-density functional (EDF) approach has been widely used to describe nuclear-matter equations of state (EoS) and properties of finite nuclei. Recent advancements in neutron-star (NS) observations have put constraints on the nuclear EoS. The Korea-IBS-Daegu-SKKU (KIDS) functional has been then developed to satisfy the NS observations and applied to homogeneous nuclear matter and spherical nuclei. Purpose: We examine the performance of the KIDS functional by calculating the masses and charge radii of even-even nuclei towards the drip lines. Method: The Kohn-Sham-Bogoliubov equation is solved by taking into account the axial deformation. Results: The root-mean-square deviation of the binding energy and the charge radius for the KIDS functional is 4.5--5.1 MeV and 0.03--0.04 fm, which is comparable to that for existing EDFs. The emergence and development of nuclear deformation in open-shell nuclei are well described. The location of the neutron drip line is according to the nuclear-matter parameter characterizing the low-mass NS. Conclusions: The NS-observation-inspired EDF offers a reasonable reproduction of the structures of finite nuclei. A future global optimization including more nuclear data will give better accuracy and high predictive power of neutron-rich nuclei.
nucl-thPRC(2023)·3 citations
03
Linear Stability of Shock Waves in Ultrarelativistic Anisotropic Hydrodynamics
Aleksandr Kovalenko🇷🇺
Linear stability of a plane shock waves in ultrarelativistic anisotropic hydrodynamics is investigated. The properties of the amplitudes of perturbations of physical quantities are studied depending on the components of the wave vector of a small harmonic perturbation. Analytical calculationsfor the longitudinal and transverse propagation of shock wave normal with respect to the anisotropy axis (beam-axis) and numerical calculations for an arbitrary polar angle are carried out.
nucl-thEPJC(2023)·1 citation
04
Investigation of the cause of the discrepancies between calculated running sums for nuclear matrix elements of two-neutrino double- $β$ decay
J. Terasaki🇨🇿
A qualitative difference in the running sum for the nuclear matrix element of the two-neutrino double- $β$ decay of $^{136}$ Xe was found four years ago between quasiparticle random-phase approximation (QRPA) and shell model calculations. The former result has large increase and decrease with respect to the excitation energy of the intermediate state, and the latter one is an almost monotonically and mildly increasing function. My QRPA calculations independently of the above one do not have a remarkable decrease. This discrepancy is a serious problem affecting the reliability of calculations of the neutrinoless double- $β$ decay, and the cause was unknown. I perform several relevant test calculations and make an analytical consideration to find the cause, which is found to be in the strength of the attractive interactions. The possible major local decrease in the running sum is also explained analytically. The interactions of my QRPA calculation are appropriate in terms of the strength, thus the almost monotonic behavior is reasonable.
nucl-thhep-exhep-phnucl-exPRC(2023)·2 citations
05
Relativistic Hartree-Fock Chiral Lagrangians with confinement, nucleon finite size and short-range effects
M. Chamseddine🇫🇷 · J. Margueron🇫🇷 · G. Chanfray🇫🇷 · H. Hansen🇫🇷 · R. Somasundaram🇺🇸
A relativistic Hartree-Fock Lagrangian including a chiral potential and nucleon polarisation is investigated in hopes of providing a better description of dense nuclear matter. We fully consider the contribution of the exchange Fock term to the energy and the self-energies, and in addition we investigate the nucleon's compositeness and finite size effects (confinement and form factors) and short range correlations modeled by a Jastrow ansatz. These effects are added step by step, such that their impact on the dense matter properties can be analysed in details. The parameters of the model are adjusted to reproduce fundamental properties related to the QCD theory at low energy, such as the chiral symmetry breaking, nucleon's quark substructure and Lattice-QCD predictions, as well as two empirical properties at saturation: the binding energy and the density. All other empirical parameters, e.g., symmetry energy and its slope, incompressibility modulus, effective mass, as well as spin-isospin Landau-Midgal parameter are predictions of the models and can be used to evaluate the gain of the different approximation schemes in describing nuclear properties. Bayesian statistics is employed in order to propagate parameter uncertainties into predictions for the nuclear matter properties. We show that the splitting of the effective Landau mass is largely influenced by the value of the $ρ^{T}$ coupling, and we show that the fit to the symmetry energy, which induces an increase of the coupling constant $g_{ρ}$ by about 20-25% compared to the case where it is fixed by the quark model, provides a very good EoS compatible with the present nuclear physics knowledge.
nucl-thEPJA(2023)·11 citations
06
Nucleosynthesis and observation of the heaviest elements
E. M. Holmbeck · T. M. Sprouse · M. R. Mumpower
The rapid neutron capture or 'r process' of nucleosynthesis is believed to be responsible for the production of approximately half the natural abundance of heavy elements found on the periodic table above iron (with proton number $Z = 26$ ) and all of the heavy elements above bismuth ( $Z = 83$ ). In the course of creating the actinides and potentially superheavies, the r process must necessarily synthesize superheavy nuclei (those with extreme proton numbers, neutron numbers or both) far from isotopes accessible in the laboratory. Many questions about this process remain unanswered, such as 'where in nature may this process occur?' and 'what are the heaviest species created by this process?' In this review, we survey at a high level the nuclear properties relevant for the heaviest elements thought to be created in the r process. We provide a synopsis of the production and destruction mechanisms of these heavy species, in particular the actinides and superheavies, and discuss these heavy elements in relation to the astrophysical r process. We review the observational evidence of actinides found in the Solar system and in metal-poor stars and comment on the prospective of observing heavy-element production in explosive astrophysical events. Finally, we discuss the possibility that future observations and laboratory experiments will provide new information in understanding the production of the heaviest elements.
nucl-thastro-ph.HEastro-ph.SREPJA(2023)·31 citations
07
Hybrid stars with reactive interfaces: analysis within the Nambu-Jona-Lasinio model
C. H. Lenzi🇧🇷 · G. Lugones🇧🇷 · C. Vasquez🇧🇷
It has been shown recently that quark-hadron conversions at the interface of a hybrid star may have a key role on the dynamic stability of the compact object. In this work we perform a systematic study of hybrid stars with reactive interfaces using a model-agnostic piecewise-polytropic hadronic equation of state and the Nambu-Jona-Lasinio model for three-flavor quark matter. For the hadronic phase we use a soft, an intermediate and a stiff parametrization that match at $1.1 n_{0}$ {with predictions} based on chiral effective field theory (cEFT) interactions. In the NJL Lagrangian we include scalar, vector and 't Hooft interactions. The vector coupling constant $g_{v}$ is treated as a free parameter. We also consider that there is a split between the deconfinement and the chiral phase transitions which is controlled by changing the conventional value of the vacuum pressure $- Ω_{0}$ in the NJL thermodynamic potential by $- (Ω_{0} + δ Ω_{0})$ , being $δ Ω_{0}$ a free parameter. We analyze the mass-radius ( $M$ - $R$ ) relation in the case of rapid ( $τ ≪ 1 ms$ ) and slow ( $τ ≫ 1 ms$ ) conversions, being $τ$ the reaction timescale. In the case of slow interface reactions we find $M$ - $R$ curves with a cusp at the maximum mass point where a pure hadronic branch and a slow-stable hybrid star (SSHS) branch coincide. We find that the length of the slow-stable branch grows with the increase of the transition density and the energy density jump at the hadron-quark interface. We calculate the tidal deformabilities of SSHSs and analyse them in the light of the GW170817 event.
nucl-thastro-ph.HEastro-ph.SRhep-phPRD(2023)·11 citations
08
Inference of the low-energy constants in $Δ$ -full chiral effective field theory including a correlated truncation error
Isak Svensson · Andreas Ekström · Christian Forssén
We sample the posterior probability distributions of the low-energy constants (LECs) in $Δ$ -full chiral effective field theory ( $χ$ EFT) up to third order. We use eigenvector continuation for fast and accurate emulation of the likelihood and Hamiltonian Monte Carlo to draw effectively independent samples from the posteriors. Our Bayesian inference is conditioned on the Granada database of neutron-proton ( $n p$ ) cross sections and polarizations. We use priors grounded in $χ$ EFT assumptions and a Roy-Steiner analysis of pion-nucleon scattering data. We model correlated EFT truncation errors using a two-feature Gaussian process, and find correlation lengths for $n p$ scattering energies and angles in the ranges 45--83 MeV and 24--39 degrees, respectively. These correlations yield a non-diagonal covariance matrix and reduce the number of independent scattering data with a factor of 8 and 4 at the second and third chiral orders, respectively. The relatively small difference between the second and third order predictions in $Δ$ -full $χ$ EFT suppresses the marginal variance of the truncation error and the effects of its correlation structure. Our results are particularly important for analyzing the predictive capabilities in \textit{ab initio} nuclear theory.
nucl-thPRC(2024)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE