Nuclear Theory·nucl-th

Wednesday·September 28, 2022

12 papers—4 primary·8 cross-listed

01
Deformation dependence of 2p-radioactivity half-lives: Probe with a new formula across the mass region with Z<82
G. Saxena · Mamta Aggarwal · D. Singh · A. Jain · P. K. Sharma · H. L. Yadav
Effect of deformation on half-life of two-proton (2p) radioactivity is investigated across the periodic chart for nuclei with Z $<$ 82. 2p-decay half-lives are estimated by employing our newly proposed semi-empirical formula wherein the nuclear deformation has been incorporated in a phenomenological way. Robustness of the formula is demonstrated as it estimates the measured values quite accurately and, hence, reliably applied to predict the other possible 2p-emitters. For many proton rich nuclei for which experimental data on the decay energies are not available, we have used the theoretical values obtained from our calculations using the relativistic mean-field (RMF) approach. The uncertainties in the theoretical decay energy values are minimised by machine learning (ML) technique. Correlation of 2p-radioactivity with 2p-halo and deformation is probed. Our calculations show the phenomenon of shape coexistence in several 2p-emitters, wherein the prolate shape is found to be more predominant for the ground state.
nucl-thJ.Phys.G(2023)·8 citations
02
Bayes goes fast: Uncertainty Quantification for a Covariant Energy Density Functional emulated by the Reduced Basis Method
Pablo Giuliani · Kyle Godbey · Edgard Bonilla · Frederi Viens · Jorge Piekarewicz
A covariant energy density functional is calibrated using a principled Bayesian statistical framework informed by experimental binding energies and charge radii of several magic and semi-magic nuclei. The Bayesian sampling required for the calibration is enabled by the emulation of the high-fidelity model through the implementation of a reduced basis method (RBM) - a set of dimensionality reduction techniques that can speed up demanding calculations involving partial differential equations by several orders of magnitude. The RBM emulator we build - using only 100 evaluations of the high-fidelity model - is able to accurately reproduce the model calculations in tens of milliseconds on a personal computer, an increase in speed of nearly a factor of 3,300 when compared to the original solver. Besides the analysis of the posterior distribution of parameters, we present predictions with properly estimated uncertainties for observables not included in the fit, specifically the neutron skin thickness of 208Pb and 48Ca, as reported by PREX and CREX collaborations. The straightforward implementation and outstanding performance of the RBM makes it an ideal tool for assisting the nuclear theory community in providing reliable estimates with properly quantified uncertainties of physical observables. Such uncertainty quantification tools will become essential given the expected abundance of data from the recently inaugurated and future experimental and observational facilities.
nucl-thphysics.comp-ph13 citations
03
Local position-space two-nucleon potentials from leading to fourth order of chiral effective field theory
S. K. Saha🇺🇸 · D. R. Entem🇪🇸 · R. Machleidt🇺🇸 · Y. Nosyk🇺🇸
We present local, position-space chiral NN potentials through four orders of chiral effective field theory ranging from leading order (LO) to next-to-next-to-next-to-leading order (N3LO, fourth order) of the Delta-less version of the theory. The long-range parts of these potentials are fixed by the very accurate pi-N LECs as determined in the Roy-Steiner equations analysis. At the highest order (N3LO), the NN data below 190 MeV laboratory energy are reproduced with the respectable chi^2/datum of 1.45. A comparison of the N3LO potential with the phenomenological Argonne v_18 (AV18) potential reveals substantial agreement between the two potentials in the intermediate range ruled by chiral symmetry, thus, providing a chiral underpinning for the phenomenological AV18 potential. Our chiral NN potentials may serve as a solid basis for systematic ab initio calculations of nuclear structure and reactions that allow for a comprehensive error analysis. In particular, the order by order development of the potentials will make possible a reliable determination of the truncation error at each order. Our new family of local position-space potentials differs from existing potentials of this kind by a weaker tensor force as reflected in relatively low D-state probabilities of the deuteron (P_D less or equal 4.0% for our N3LO potentials) and predictions for the triton binding energy above 8.00 MeV (from two-body forces alone). As a consequence, our potentials may lead to different predictions when applied to light and intermediate-mass nuclei in ab initio calculations and, potentially, help solve some of the outstanding problems in microscopic nuclear structure.
nucl-thnucl-exPRC(2023)·29 citations
04
Elastic properties of nuclear pasta in a fully three-dimensional geometry
Cheng-Jun Xia · Toshiki Maruyama · Nobutoshi Yasutake · Toshitaka Tatsumi · Ying-Xun Zhang
Realistic estimations on the elastic properties of neutron star matter are carried out with a large strain ( $ε ≲ 0.5$ ) in the framework of relativistic-mean-field model with Thomas-Fermi approximation, where various crystalline configurations are considered in a fully three-dimensional geometry with reflection symmetry. Our calculation confirms the validity of assuming Coulomb crystals for the droplet phase above neutron drip density, which nonetheless does not work at large densities since the elastic constants are found to be decreasing after reaching their peaks. Similarly, the analytic formulae derived in the incompressible liquid-drop model give excellent description for the rod phase at small densities, which overestimates the elastic constants at larger densities. For slabs, due to the negligence on the variations of their thicknesses, the analytic formulae from liquid-drop model agree qualitatively but not quantitatively with our numerical estimations. By fitting to the numerical results, these analytic formulae are improved by introducing dampening factors. The impacts of nuclear symmetry energy are examined adopting two parameter sets, corresponding to the slope of symmetry energy $L = 41.34$ and 89.39 MeV. Even with the uncertainties caused by the anisotropy in polycrystallines, the elastic properties of neutron star matter obtained with $L = 41.34$ and 89.39 MeV are distinctively different, results in detectable differences in various neutron star activities.
nucl-thastro-ph.HEPLB(2023)·11 citations
05
Valleytronic full configuration-interaction approach: An application to the excitation spectra of Si double-dot qubits
Constantine Yannouleas🇺🇸 · Uzi Landman🇺🇸
The influence of strong electron-electron interactions and Wigner-molecule (WM) formation on the spectra of $2 e$ singlet-triplet double-dot Si qubits is presented based on a full configuration interaction (FCI) approach that incorporates the valley degree of freedom (VDOF) in the context of the continuous (effective mass) description of semiconductor materials. Our FCI treats the VDOF as an isospin in addition to the regular spin. Our treatment is able to assign to each energy curve in the qubit's spectrum a complete set of good quantum numbers for both the spin and the valley isospin. This reveals an underlying SU(4) $\supset$ SU(2) $\times$ SU(2) group-chain organization in the Si double-dot spectra. With parameters in the range of actual experimental situations, we demonstrate in a double-dot qubit that, in the (2,0) charge configuration and compared to the expected large, and dot-size determined, single-particle (orbital) energy gap, the strong $e - e$ interactions drastically quench the spin-singlet $-$ spin-triplet energy gap, $E_{ST}$ , within the same valley, making it competitive to the small energy gap, $E_{V}$ , between the two valleys. We present results for both the $E_{ST} < E_{V}$ and $E_{ST} > E_{V}$ cases. We investigate the spectra as a function of detuning and demonstrate the strengthening of the avoided crossings due to a lowering of the interdot barrier and/or the influence of valley-orbit coupling. We further demonstrate, as a function of an applied magnetic field, the emergence of avoided crossings in the (1,1) charge configuration due to the spin-valley coupling. The valleytronic FCI formulated here, and implementeded for two electrons confined in a tunable double quantum dot, offers also a most effective tool for analyzing the spectra of Si qubits with more than two wells and/or more than two electrons.
↳ cond-mat.mes-hallnucl-thquant-phPRB(2022)·9 citations
06
Discovering QCD-Coupled Axion Dark Matter with Polarization Haloscopes
Asher Berlin🇺🇸 · Kevin Zhou🇺🇸
In the presence of QCD axion dark matter, atoms acquire time-dependent electric dipole moments. This effect gives rise to an oscillating current in a nuclear spin-polarized dielectric, which can resonantly excite an electromagnetic mode of a microwave cavity. We show that with existing technology such a "polarization haloscope" can explore orders of magnitude of new parameter space for QCD-coupled axions. If any cavity haloscope detects a signal from the axion-photon coupling, an upgraded polarization haloscope has the unique ability to test whether it arises from the QCD axion.
↳ hep-phhep-exnucl-thphysics.ins-detPRD(2023)·21 citations
07
Four-quark scatterings in QCD I
Wei-jie Fu🇨🇳 · Chuang Huang🇨🇳 · Jan M. Pawlowski🇩🇪 · Yang-yang Tan🇨🇳
We investigate dynamical chiral symmetry breaking and the emergence of mesonic bound states from the infrared dynamics of four-quark scatterings. Both phenomena originate from the resonant scalar-pseudoscalar channel of the four-quark scatterings, and we compute the functional renormalisation group (fRG) flows of the Fierz-complete four-quark interaction of up and down quarks with its $t$ channel momentum dependence. This is done in the isospin symmetric case, also including the flow of the quark two-point function. This system can be understood as the fRG analogues of the complete Bethe-Salpeter equations and quark gap equation. The pole mass of the pion is determined from both direct calculations of the four-quark flows in the Minkowski regime of momenta and the analytic continuation based on results in the Euclidean regime, which are consistent with each other.
↳ hep-phnucl-thSciPost Phys.(2023)·31 citations
08
$U_{A} (1)$ symmetry restoration at high baryon density
Jianing Li🇨🇳 · Jin Gui🇨🇳 · Pengfei Zhuang🇨🇳
We study the relation between chiral and $U_{A} (1)$ symmetries in the quark-meson model. Although quarks and mesons are described in mean field approximation, the topological susceptibility characterizing the $U_{A} (1)$ breaking comprises two components: one controlled by the condensate and the other by the meson fluctuation. The $U_{A} (1)$ restoration is governed by the competition of these components. In a hot medium, the condensates melt. However, the fluctuation is enhanced. Therefore, the $U_{A} (1)$ symmetry cannot be solely restored via the temperature effect. Nevertheless, the baryon density reduces the condensates and fluctuation, and thereby, the $U_{A} (1)$ symmetry can only be restored in a dense or dense and hot medium. The strange condensate plays a weak role in the susceptibility, and the chiral and $U_{A} (1)$ symmetry restorations occur almost at the same critical point.
↳ hep-phnucl-thCPC(2023)·3 citations
09
BiFold: A Python code for the calculation of double folded (bifold) potentials with density-in/dependent nucleon-nucleon interactions
Mesut Karakoç
BiFold calculates the density-dependent (DDM3Y $n$ , BDM3Y $n$ , CDM3Y $n$ ) or independent double folded potentials between two colliding spherical nuclei. It is written in a Python package form to give the ability to use the potentials directly in a nuclear reaction/structure code. In addition to using Woods-Saxon/Fermi or Gaussian functions, the code also allows for the definition of nuclear matter densities using pre-calculated densities in a data file. The manuscript provides an overview of the double folding model and the use of the code.
↳ physics.comp-phnucl-thComput.Phys.Commun.(2023)·9 citations
10
Bottom hadro-chemistry in high-energy hadronic collisions
Min He🇨🇳 · Ralf Rapp🇺🇸
The hadro-chemistry of bottom quarks ( $b$ ) produced in hadronic collisions encodes valuable information on the mechanism of color-neutralization in these reactions. Since the $b$ -quark mass is much larger than the typical hadronic scale of $\sim$ 1\,GeV, $b b ˉ$ pair production is expected to be well separated from subsequent hadronization processes. A significantly larger fraction of $b$ baryons has been observed in proton-proton ( $pp$ ) and proton-antiproton ( $p p ˉ$ ) reactions relative to $e^{+} e^{-}$ collisions, challenging theoretical descriptions. We address this problem by employing a statistical hadronization approach with an augmented set of $b$ -hadron states beyond currently measured ones, guided by the relativistic quark model and lattice-QCD computations. Assuming {\it relative} chemical equilibrium between different $b$ -hadron yields, thermal densities are used as fragmentation weights of $b$ -quarks into various hadron species. With quark model estimates of the decay patterns of excited states, the fragmentation fractions of weakly-decaying $b$ hadrons are computed and found to agree with measurements in $p p ˉ$ collisions at the Tevatron. By combining transverse-momentum ( $p_{T}$ ) distributions of $b$ -quarks from perturbative QCD with thermal weights and independent fragmentation toward high $p_{T}$ , a fair description of the $p_{T}$ -dependent $B ˉ_{s}^{0} / B^{-}$ and $Λ_{b}^{0} / B^{-}$ ratios measured in $pp$ collisions at the LHC is obtained. Finally, we implement the hadro-chemistry into a strongly-coupled transport approach for $b$ -quarks in heavy-ion collisions, utilizing previously determined $b$ -quark transport coefficients in the Quark-Gluon Plasma, to highlight the modifications of hadro-chemistry and collective behavior of $b$ hadrons in Pb-Pb collisions at the LHC.
↳ hep-phhep-exnucl-exnucl-thPRL(2023)·32 citations
11
$B_{c}$ enhancement with non-thermalized bottom quarks in nuclear collisions at Large Hadron Collider
Jiaxing Zhao🇨🇳 · Pengfei Zhuang🇨🇳
We study $B_{c}$ production in high-energy nuclear collisions in a transport approach with dissociation and regeneration at finite temperatures. Due to the rare production in p+p collisions and the strong combination of uncorrelated $c$ and $b ˉ$ quarks in the quark-gluon plasma, the $B_{c}$ yield is significantly enhanced in the nuclear collisions at the Large Hadron Collider. Moreover, the centrality and momentum-dependent yield of $B_{c}$ sensitively reflect the thermalization degree of bottom quarks. And the newly observed experimental data favors a far from the thermal bottom quark distribution in the quark-gluon plasma.
↳ hep-phnucl-thEPJA(2025)·5 citations
12
Rotating Solar Models in Agreement with Helioseismic Results and Updated Neutrino Fluxes
Wuming Yang
Standard solar models (SSMs) constructed in accordance with old solar abundances are in reasonable agreement with seismically inferred results, but SSMs with new low-metal abundances disagree with the seismically inferred results. The constraints of neutrino fluxes on solar models exist in parallel with those of helioseismic results. The solar neutrino fluxes were updated by Borexino Collaboration. We constructed rotating solar models with new low-metal abundances where the effects of enhanced diffusion and convection overshoot were included. A rotating model using OPAL opacities and the Caffau abundance scale has better sound-speed and density profiles than the SSM with the old solar abundances and reproduces the observed $p$ -mode frequency ratios $r_{02}$ and $r_{13}$ . The depth and helium abundance of the convection zone of the model agree with the seismically inferred ones at the level of $1 σ$ . The updated neutrino fluxes are also reproduced by the model at the level of $1 σ$ . The effects of rotation and enhanced diffusion not only improve the model's sound-speed and density profiles but bring the neutrino fluxes predicted by the model into agreement with the detected ones. Moreover, the calculations show that OP may underestimate opacities for the regions of the Sun with $T ≳ 5 \times 1 0^{6}$ K by around $1.5%$ , while OPAL may underestimate opacities for the regions of the Sun with $2 \times 1 0^{6}$ K $≲ T ≲ 5 \times 1 0^{6}$ K by about $1 - 2%$ .
↳ astro-ph.SRnucl-thApJ(2022)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE