Nuclear Theory·nucl-th

Tuesday·June 28, 2022

16 papers—9 primary·7 cross-listed

01
Spatial correlation of a particle-hole pair with a repulsive isovector interaction
K. Hagino · H. Sagawa
We study the spatial correlation of a particle-hole pair in the isovector channel in $^{56}$ Co and $^{40}$ K nuclei. To this end, we employ the Hartree-Fock+Tamm-Dancoff approximation with the Skyrme interaction. We find a large concentration of the two-body density at positions where the neutron particle and the proton hole states locate on the opposite side to each other with respect to the core nucleus. This feature originates from a repulsive nature of the isovector residual interaction, which is in stark contrast to the dineutron correlation with an attractive pairing interaction between the valence neutrons discussed e.g., in $^{11}$ Li and $^{6}$ He. A possible experimental implication of the repulsive correlation is also discussed.
nucl-thnucl-exPRC(2022)·1 citation
02
The Hadron-Quark Crossover in Neutron Star within Gaussian Process Regression Method
Kaixuan Huang🇨🇳 · Jinniu Hu🇨🇳 · Ying Zhang🇨🇳 · Hong Shen🇨🇳
The equations of state of the neutron star at the hadron-quark crossover region are interpolated with the Gaussian process regression (GPR) method, which can reduce the randomness of present interpolation schemes. The relativistic mean-field (RMF) model and Nambu-Jona-Lasinio (NJL) model are employed to describe the hadronic phase and quark phase, respectively. In the RMF model, the coupling term between $ω$ and $ρ$ mesons is considered to control the density-dependent behaviors of symmetry energy, i.e. the slope of symmetry energy, $L$ . Furthermore, the vector interaction between quarks is included in the NJL model to obtain the additional repulsive contributions. Their coupling strengths and the crossover windows are discussed in the present framework under the constraints on the neutron star from gravitational wave detections, massive neutron star measurements, mass-radius simultaneous observation of NICER collaboration, and the neutron skin thickness of $^{208}$ Pb from PREX-II. It is found that the slope of symmetry energy, $L$ should be around $50 - 90$ MeV and the crossover window is $(0.3, 0.6) f m^{- 3}$ with these observables. Furthermore, the uncertainties of neutron star masses and radii in the hadron-quark crossover regions are also predicted by the GPR method.
nucl-thApJ(2022)·21 citations
03
Hydrodynamic attractor of noisy plasmas
Zenan Chen🇨🇳 · Derek Teaney🇨🇳 · Li Yan🇨🇳
We provide a generalized formulation of fluctuating hydrodynamics for the far-from-equilibrium noisy medium. As an example, we consider a noisy plasma experiencing Bjorken expansion, for which the leading order evolution is captured by hydrodynamic attractor of classical hydrodynamics, while the quadratic couplings of fluctuations are solved effectively via a generalized version of the hydrodynamic kinetic equation. In the far-from-equilibrium plasma, backreaction of hydrodynamic fluctuations results in renormalization of transport properties, as well as long time tails, of high orders. In particular, corresponding to a renormalized hydrodynamic attractor, evolution in a noisy plasma towards equilibrium becomes non-monotonic.
nucl-thhep-phPRC(2023)·9 citations
04
Nuclear charge radii in Bayesian neural networks revisited
Xiao-Xu Dong · Rong An · Jun-Xu Lu · Li-Sheng Geng
In this work, a refined Bayesian neural network (BNN) based approach with six inputs including the proton number, mass number, and engineered features associated with the pairing effect, shell effect, isospin effect, and ``abnormal" shape staggering effect of $^{181, 183, 185}$ Hg, is proposed to accurately describe nuclear charge radii. The new approach is able to well describe the charge radii of atomic nuclei with $A \geq 40$ and $Z \geq 20$ . The standard root-mean-square (rms) deviation is $0.014$ fm for both the training and validation data. In particular, the predicted charge radii of proton-rich and neutron-rich calcium isotopes are found in good agreement with data. We further demonstrate the reliability of the BNN approach by investigating the variations of the rms deviation with extrapolation distances, mass numbers, and isospin asymmetries.
nucl-thnucl-exPLB(2023)·54 citations
05
Conserving approximations to dilute equilibrium systems. Pair interaction potential
E.E. Kolomeitsev · P.D. Lukianov · D.N. Voskresensky
We study self-consistent approximations such as the $Φ$ -derivable and virial approaches to dilute strongly interacting systems in equilibrium. We consider a system of non-relativistic fermions of one kind interacting via a pair potential Thermodynamical quantities are expressed in terms of various spectral functions. We review the $Φ$ derivable approximation scheme demonstrating the exact conservation of the Noether and the Botermans-Malfliet fermion number densities, and then for $Φ$ described by the tadpole and sandwich diagrams we show the coincidence of these two number densities. As examples of test pair potentials, we consider the Yukawa central nucleon-nucleon potentials within Walecka, CD Bonn, and Reid parameterizations, and the corresponding classical Lennard-Jones potentials. Expressions for the second and third virial coefficients are derived and analyzed for $Φ$ described by the tadpole and sandwich diagrams. Next, we focus on the virial approach to the equation of state. Classical, semiclassical, and purely quantum approaches are studied in detail. Then, different extrapolations of the virial equation of state are considered including the van~der~Waals form and excluded-volume models. We derive the expression for the second virial coefficient using the effective range approximation for the scattering amplitude and compare the result with the purely quantum result using the experimental phase shifts. Attention is focused on the problem of anomalously large value of the nucleon-nucleon scattering length appearing due to the presence of the quasi-bound state in nucleon-nucleon scattering, which can be destroyed in the matter because of the action of the Pauli blocking. We present results for the second virial coefficient subtracting this term. We discuss the validity of such a procedure to describe the equation of state of the nuclear matter in the virial limit.
nucl-thastro-ph.HEnucl-exPhys.Part.Nucl.(2024)·1 citation
06
Potential energy surface and formation of superheavy nuclei with the Skyrme energy-density functional
Cheng Peng · Zhao-Qing Feng
Within the framework of Skyrme energy-density functional theory, the nucleus-nucleus potential is calculated and potential energy surface is obtained with different effective forces for accurately estimating the formation cross sections of superheavy nuclei in massive fusion reactions. The width and height of the potential pocket are influenced by the Skyrme effective forces SkM, SkM $^{*}$ , SkP, SIII, Ska and SLy4, which correspond to the different equation of state for the isospin symmetry nuclear matter. It is found that the nucleus-nucleus potential is associated with the collision orientation and Skyrme parameters. More repulsive nuclear potential is pronounced with increasing the incompressible modulus of nuclear matter. The available data in the fusion-evaporation reaction of $^{48}$ Ca+ $^{238}$ U are nicely reproduced with the SkM $^{*}$ parameter by implementing into the dinuclear system model.
nucl-thCommun.Theor.Phys.(2022)·3 citations
07
Relativistic effects and three-body interactions in atomic nuclei
Y. L. Yang · P. W. Zhao
Based on the leading-order covariant pionless effective field theory, a relativistic nuclear Hamiltonian is derived and solved using the variational Monte Carlo approach for $A \leq 4$ nuclei by representing the nuclear many-body wave functions with a symmetry-based artificial neural network. It is found that the relativistic effects rescue the renormalizability of the theory, and overcome the energy collapse problem for $^{3}$ H and $^{4}$ He without promoting a repulsive three-nucleon interaction to leading order as in nonrelativistic calculations. Nevertheless, to exactly reproduce the experimental ground-state energies, a three-nucleon interaction is needed and its interplay with the relativistic effects plays a crucial role. The strongly repulsive relativistic effects suppress the energy contribution given by the three-nucleon interactions, so a strong strength for the three-nucleon interaction could be required to reproduce the experimental energies. These results shed light on a consistent understanding of relativistic effects and three-body interactions in atomic nuclei.
nucl-thPLB(2022)·38 citations
08
Nuclear properties with semilocal momentum-space regularized chiral interactions beyond N2LO
P. Maris🇺🇸 · R. Roth🇩🇪 · E. Epelbaum🇩🇪 · R.J. Furnstahl🇺🇸 · J. Golak🇵🇱 · K. Hebeler🇩🇪 · T. Hüther🇩🇪 · H. Kamada🇯🇵 · H. Krebs🇩🇪 · H. Le🇩🇪 · Ulf-G. Meißner🇩🇪 · J.A. Melendez🇺🇸 and 6 other authors
We present a comprehensive investigation of few-nucleon systems as well as light and medium-mass nuclei up to $A = 48$ using the current Low Energy Nuclear Physics International Collaboration two-nucleon interactions in combination with the third-order (N $^{2}$ LO) three-nucleon forces. To address the systematic overbinding of nuclei starting from $A \sim 10$ found in our earlier study utilizing the N $^{2}$ LO two- and three-nucleon forces, we take into account higher-order corrections to the two-nucleon potentials up through fifth order in chiral effective field theory. The resulting Hamiltonian can be completely determined using the $A = 3$ binding energies and selected nucleon-deuteron cross sections as input. It is then shown to predict other nucleon-deuteron scattering observables and spectra of light $p$ -shell nuclei, for which a detailed correlated truncation error analysis is performed, in agreement with experimental data. Moreover, the predicted ground state energies of nuclei in the oxygen isotopic chain from $^{14}$ O to $^{26}$ O as well as $^{40}$ Ca and $^{48}$ Ca show a remarkably good agreement with experimental values, given that the Hamiltonian is fixed completely from the $A \leq 3$ data, once the fourth-order (N $^{3}$ LO) corrections to the two-nucleon interactions are taken into account. On the other hand, the charge radii are found to be underpredicted by $\sim 10%$ for the oxygen isotopes and by almost $20%$ for $^{40}$ Ca and $^{48}$ Ca.
nucl-thPRC(2022)·62 citations
09
Emergence of $^{4}$ H $J^{π} = 1^{-}$ resonance in contact theories
Lorenzo Contessi🇫🇷 · Martin Schäfer🇮🇱 · Johannes Kirscher🇮🇳 · Rimantas Lazauskas🇫🇷 · Jaume Carbonel🇫🇷
We obtain the $s$ - and $p$ -wave low-energy scattering parameters for n $^{3}$ H elastic scattering and the position of the $^{4}$ H $J^{π} = 1^{-}$ resonance using the pionless effective field theory at leading order. Results are extracted with three numerical techniques: confining the system in a harmonic oscillator trap, solving the Faddeev-Yakubovsky equations in configuration space, and using an effective two-body cluster approach. The renormalization of the theory for the relevant amplitudes is assessed in a cutoff-regulator range between $1 fm^{- 1}$ and $10 fm^{- 1}$ . Most remarkably, we find a cutoff-stable/RG-invariant resonance in the $^{4}$ H $J^{π} = 1^{-}$ system. This $p$ -wave resonance is a universal consequence of a shallow two-body state and the introduction of a three-body $s$ -wave scale set by the triton binding energy. The stabilization of a resonant state in a few-fermion system through pure contact interactions has a significant consequence for the powercounting of the pionless theory. Specifically, it suggests the appearance of similar resonant states also in larger nuclei, like 16-oxygen, in which the theory's leading order does not predict stable states. Those resonances would provide a starting state to be moved to the correct physical position by the perturbative insertion of sub-leading orders, possibly resolving the discrepancy between data and contact EFT.
nucl-thphysics.atom-phPLB(2023)·6 citations
10
Nucleon axial form factor at large momentum transfers
Chen Chen🇨🇳 · Craig D. Roberts🇨🇳
Using a Poincaré-covariant quark+diquark Faddeev equation and related symmetry-preserving weak interaction current, we deliver parameter-free predictions for the nucleon axialvector form factor, $G_{A} (Q^{2})$ , on the domain $0 \leq x = Q^{2} / m_{N}^{2} \leq 10$ , where $m_{N}$ is the nucleon mass. We also provide a detailed analysis of the flavour separation of the proton $G_{A}$ into contributions from valence $u$ and $d$ quarks; and with form factors available on such a large $Q^{2}$ domain, predictions for the flavour-separated axial-charge light-front transverse spatial density profiles. Our calculated axial charge ratio $g_{A}^{d} / g_{A}^{u} = - 0.32 (2)$ is consistent with available experimental data and markedly larger in magnitude than the value typical of nonrelativistic quark models. The value of this ratio is sensitive to the strength of axialvector diquark correlations in the Poincaré-covariant nucleon wave function. Working with a realistic axialvector diquark content, the $d$ and $u$ quark transverse density profiles are similar. Some of these predictions could potentially be tested with new data on threshold pion electroproduction from the proton at large $Q^{2}$ .
↳ hep-phhep-exhep-latnucl-ex+1EPJA(2022)·22 citations
11
Shear induced polarization: Collisional contributions
Shu Lin🇨🇳 · Ziyue Wang🇨🇳
It has been realized that thermal shear plays a similar role as thermal vorticity in polarizing spin of particles in heavy ion collisions. We point out that shear has a fundamental difference that it leads to particle redistribution in the medium. The redistribution gives rise to an additional contribution to spin polarization through the self-energy, which is parametrically the same order as the one considered so far in the literature. The self-energy contribution is in general gauge dependent. We introduce double gauge links stretching along the Schwinger-Keldysh contour to restore gauge invariance. We also generalize the straight path to adapt to the Schwinger-Keldysh contour. We find another contribution associated with the gauge link, which is also parametrically the same order. We illustrate the two contributions with a massive probe fermion in massless QED plasma with shear. A modest suppression of spin polarization is found from the combined contributions when the probe fermion has momentum much greater than the temperature.
↳ hep-phcond-mat.mes-hallnucl-exnucl-thJHEP(2022)·32 citations
12
Role of the effective range in the density-induced BEC-BCS crossover
Hiroyuki Tajima · Haozhao Liang
We elucidate the role of the effective range in the Bose-Einstein-condensate (BEC) to Bardeen-Cooper-Schrieffer (BCS) crossover regime of two-component fermions in three dimensions. In contrast to ultracold Fermi gases near the broad Feshbach resonance, where the interaction can be characterized by the contact-type interaction, the interaction range in general becomes important in the density-induced BEC-BCS crossover discussed in the context of condensed-matter and nuclear systems. Characterizing the non-local interaction in terms of the low-energy constants such as scattering length $a$ and effective range $r$ , we show how the crossover phenomena are affected by nonzero effective ranges. In particular, we show that the superfluid order parameter is strongly suppressed in the high-density regime and the sound velocity exhibits a non-monotonic behavior reflecting mechanical stability of the system. Moreover, we point out that the high-momentum tail associated with the contact parameter can be visible when the magnitude of momentum $k$ is much less than $1/ r$ .
↳ cond-mat.quant-gascond-mat.supr-connucl-thPRA(2022)·8 citations
13
Minkowski's lost legacy and hadron electromagnetism
Yang Li🇨🇳 · Wen-bo Dong🇨🇳 · Yi-liang Yin🇨🇳 · Qun Wang🇨🇳 · James P. Vary🇺🇸
We revisit Minkowski's lost legacy on relativistic electromagnetism in order to resolve long-standing puzzles over the charge distribution of relativistic systems like hadrons. Hadrons are unique relativistic electromagnetic systems characterized by their comparable size and Compton wavelength $r_{h} \sim λ_{C}$ . As such, it was recently realized that the traditional Sachs definition of the charge distribution based on a non-relativistic formula is invalid. We explain that this is the same problem pursued by Lorentz, Einstein and others, on the electromagnetism of a moving body. We show how various charge distributions proposed in hadronic physics naturally emerge as the multipole moment densities in the macroscopic theory of relativistic electromagnetism.
↳ hep-phnucl-thphysics.class-phquant-phPLB(2023)·21 citations
14
Three-body continuum states and Efimov physics in non-integer geometry
E. Garrido · E.R. Christensen · A.S. Jensen
Continuum structures of three short-range interacting particles in a deformed external one-body field are investigated. We use the equivalent $d$ -method employing non-integer dimension, $d$ , in a spherical calculation with a dimension-dependent angular momentum barrier. We focus on dimensions close to the critical dimension, $d = d_{E}$ , between two and three, defined by zero two-body energies, where the Efimov effect can occur. We design for this dimension region a schematic, long-distance realistic, square-well based, three-body spherical model, which is used to derive analytic expressions for the wave functions, scattering lengths, phase shifts, and elastic scattering cross sections. The procedure and the results are universal, valid for all short-range potentials, and for large scattering lengths. We discuss the properties and validity of the derived expressions by means of the simplest system of three identical bosons. The derived expressions are particularly useful for very small energies, where full numerical calculations are often not feasible. For energies where the numerical calculations can be performed, a good agreement with the analytic results is found. These model results may be tested by scattering experiments for three particles in an equivalent external deformed oscillator potential. The cross sections all vanish in the zero-energy limit for $d < 3$ with definite $d$ -dependent power of energy.
↳ physics.atom-phcond-mat.quant-gasnucl-thPRA(2022)·3 citations
15
Nonperturbative effects in neutrino magnetic moments
Feng-Zhi Chen🇨🇳 · Min-Di Zheng🇨🇳 · Hong-Hao Zhang🇨🇳
In this paper, we calculate the QCD nonperturbative contributions of the neutrino-quark tensor operators to the neutrino magnetic moments by matching onto the chiral perturbation theory at low energies. These nonperturbative contributions can be compared to the perturbative ones, which are induced from one-loop mixing when performing the renormalization group evolutions from $μ = m_{W}$ down to $μ = 2 GeV$ . We then constrain the dipole and tensor Wilson coefficients of the low-energy neutrino effective field theory (LNEFT) separately from the neutrino-electron scattering with Borexino data and coherent elastic neutrino-nucleus scattering (CE $ν$ NS) with COHERENT data to show the competition between these two contributions, at the renormalization scales $μ = 2 GeV$ and $μ = m_{W}$ in the $MS ˉ$ scheme. In the neutrino-electron scattering, it is found that the nonperturbative contributions dominate for the coefficients involving up and down quarks, while they are expected to be of the same order of magnitude as the perturbative contributions for the coefficients involving strange quark. As for constraints in the CE $ν$ NS, the tensor operators can contribute to the process through either direct or indirect way. As a result, the indirect contributions including nonperturbative and perturbative parts for all couplings become negligible in comparison with the direct ones. As the nonperturbative contributions crucially depend on the value of $c_{T}$ , its inputs will affect the extraction of limits on the tensor LNEFT Wilson coefficients. We compute the upper bounds on these coefficients with $c_{T}$ quoting from the model and lattice estimates.
↳ hep-phnucl-thPRD(2022)·4 citations
16
Diffractive deep inelastic scattering at NLO in the dipole picture: the $q q ˉ g$ contribution
G. Beuf🇵🇱 · H. Hänninen🇫🇮 · T. Lappi🇫🇮 · Y. Mulian🇪🇸 · H. Mäntysaari🇫🇮
We calculate the contribution from the $q q ˉ g$ state production to the diffractive cross sections in deep inelastic scattering at high energy. The obtained cross section is finite by itself and a part of the full next-to-leading order result for the diffractive structure functions. We perform the calculation in exact kinematics in the eikonal limit, and show that the previously known high- $Q^{2}$ and large $M_{X}^{2}$ results for the structure functions can be extracted from our results in the appropriate limits. We furthermore discuss the steps required to obtain the full next-to-leading order results for the structure functions.
↳ hep-phnucl-thPRD(2022)·51 citations

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first authorsco-authorsvia INSPIRE