Nuclear Theory·nucl-th

Tuesday·May 18, 2021

15 papers—10 primary·5 cross-listed

01
[Submitted on 14 May 2021]
Matrix-product state approach to the generalized nuclear pairing Hamiltonian
Roman Rausch🇩🇪 · Cassian Plorin🇩🇪 · Matthias Peschke🇳🇱 · Christoph Karrasch🇩🇪
We show that from the point of view of the generalized pairing Hamiltonian, the atomic nucleus is a system with small entanglement and can thus be described efficiently using a 1D tensor network (matrix-product state) despite the presence of long-range interactions. The ground state can be obtained using the density-matrix renormalization group (DMRG) algorithm, which is accurate up to machine precision even for large nuclei, is numerically as cheap as the widely used BCS (Bardeen-Cooper-Schrieffer) approach, and does not suffer from any mean-field artifacts. We apply this framework to compute the even-odd mass differences of all known lead isotopes from $^{178}$ Pb to $^{220}$ Pb in a very large configuration space of 13 shells between the neutron magic numbers 82 and 184 (i.e., two major shells) and find good agreement with the experiment. We also treat pairing with non-zero angular momentum and determine the lowest excited states in the full configuration space of one major shell, which we demonstrate for the $N = 126$ , $Z \geq 82$ isotones. To demonstrate the capabilities of the method beyond low-lying excitations, we calculate the first 100 excited states of $^{208}$ Pb with singlet pairing and the two-neutron removal spectral function of $^{210}$ Pb, which relates to a two-neutron pickup experiment.
Subjects:
Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el)
arXiv:
2105.07012 [pdf]
Annalen Phys.(2024)·2 citations
02
[Submitted on 15 May 2021]
Derivation of the Grodzins relation in collective nuclear model
R.V. Jolos · E.A. Kolganova
Basing on the Bohr collective quadrupole Hamiltonian the $A$ -dependence of the Grodzins product is derived and the proportionality coefficient for the Grodzins relation is evaluated. The result obtained is in a correspondence with the experimental data.
Comments:
7 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.07164 [pdf]
PLB(2021)·6 citations
03
[Submitted on 15 May 2021]
Neutron--proton spin--spin correlations in the ground states of N=Z nuclei
P. Van Isacker🇫🇷 · A. O. Macchiavelli🇺🇸
We present expressions for the matrix elements of the spin--spin operator $S_{n} \cdot S_{p}$ in a variety of coupling schemes. These results are then applied to calculate the expectation value $⟨ S_{n} \cdot S_{p} ⟩$ in eigenstates of a schematic Hamiltonian describing neutrons and protons interacting in a single- $l$ shell through a Surface Delta Interaction. The model allows us to trace $⟨ S_{n} \cdot S_{p} ⟩$ as a function of the competition between the isovector and isoscalar interaction strengths and the spin--orbit splitting of the $j = l \pm \frac{1}{2}$ shells. We find negative $⟨ S_{n} \cdot S_{p} ⟩$ values in the ground state of all even--even $N = Z$ nuclei, contrary to what has been observed in hadronic inelastic scattering at medium energies. We discuss the possible origin of this discrepancy and indicate directions for future theoretical and experimental studies related to neutron--proton spin--spin correlations.
Comments:
11 pages, 7 figures. Accepted for publication in the European Physical Journal A
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.07267 [pdf]
EPJA(2021)·7 citations
04
[Submitted on 17 May 2021]
Continuum random-phase approximation for gamma transition between excited states in neutron-rich nuclei
Teruyuki Saito🇯🇵 · Masayuki Matsuo🇯🇵
A characteristic feature of collective and particle-hole excitations in neutron-rich nuclei is that many of them couple to unbound neutron in continuum single-particle orbits. The continuum random phase approximation (cRPA) is a powerful many-body method that describes such excitations, and it provides a scheme to evaluate transition strengths from the ground state. In an attempt to apply cRPA to the radiative neutron capture reaction, we formulate in the present study an extended scheme of cRPA that describes gamma-transitions from the excited states under consideration, which decay to low-lying excited states as well as the ground state. This is achieved by introducing a non-local one-body operator which causes transitions to a low-lying excited state, and describing a density-matrix response against this operator. As a demonstration of this new scheme, we perform numerical calculation for dipole, quadrupole, and octupole excitations in $^{140}$ Sn, and discuss E1 and E2 transitions decaying to low-lying $2_{1, 2}^{+}$ and $3_{1}^{-}$ states. The results point to cases where the branching ratio to the low-lying states is larger than or comparable with that to the ground state. We discuss key roles of collectivity and continuum orbits in both initial and final states.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.07586 [pdf]
PRC(2021)·4 citations
05
[Submitted on 17 May 2021]
Structure of $^{46, 47}$ Ca from the $β^{-}$ decay of $^{46, 47}$ K in the framework of nuclear shell model
Priyanka Choudhary🇮🇳 · Anil Kumar🇮🇳 · Praveen C. Srivastava🇮🇳 · Toshio Suzuki🇯🇵
In the present work, we report a comprehensive theoretical study of the $lo g f t$ values for the allowed and forbidden $β^{-}$ decay transitions of $^{46}$ K and $^{47}$ K corresponding to recently available experimental data from the GRIFFIN spectrometer at TRIUMF-ISAC [Phys. Rev. C {\bf 100}, 054327 (2019); Phys. Rev. C {\bf 102}, 054314 (2020)]. We perform the nuclear shell-model calculation in $s d p f$ -valence space, with the SDPF-MU interaction, to calculate low-lying energy spectra of $^{46, 47}$ K and $^{46, 47}$ Ca. For further investigation, we also calculate spectroscopic properties of $^{46, 47}$ K, $^{46, 47}$ Ca and compare the results with the experimental data. We suggest spin-parity of several levels, which were previously tentative, in both the calcium isotopes. Based on the energy and $lo g f t$ values, we conclude that the state at 3.984 MeV in $^{46}$ Ca could be either $3^{-}$ or $2^{+}$ and a state at 4.432 MeV might be $3^{-}$ . The spin-parity of the states at 2.875, 3.951 and 4.453 MeV are predicted to be $1/ 2^{-}$ , $3/ 2^{-}$ and $1/ 2^{-}$ or $1/ 2^{+}$ , respectively, in $^{47}$ Ca. We also give the confirmation to spin-parity of 2.850, 3.889 and 4.606 MeV states for $^{47}$ Ca. Our results of level schemes of $^{46, 47}$ K are in a reasonable agreement with the experimental data, while the agreement of calculated $lo g f t$ values for the $β^{-}$ decay with the experimental data is limited.
Comments:
11 pages, 4 figures, 5 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.07662 [pdf]
PRC(2021)·11 citations
06
[Submitted on 17 May 2021]
Nuclear energy density functionals from machine learning
X. H. Wu🇨🇳 · Z. X. Ren🇨🇳 · P. W. Zhao🇨🇳
Machine learning is employed to build an energy density functional for self-bound nuclear systems for the first time. By learning the kinetic energy as a functional of the nucleon density alone, a robust and accurate orbital-free density functional for nuclei is established. Self-consistent calculations that bypass the Kohn-Sham equations provide the ground-state densities, total energies, and root-mean-square radii with a high accuracy in comparison with the Kohn-Sham solutions. No existing orbital-free density functional theory comes close to this performance for nuclei. Therefore, it provides a new promising way for future developments of nuclear energy density functionals for the whole nuclear chart.
Comments:
6 pages, 3 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2105.07696 [pdf]
PRC(2022)·46 citations
07
[Submitted on 17 May 2021]
Incompressibility and Symmetry Energy of Neutron Star
Ankit Kumar🇮🇳 · H. C. Das🇮🇳 · S. K. Patra🇮🇳
We trace a systematic and consistent method to precisely numerate the magnitude range for various structural and isospin compositional properties of the neutron star. Incompressibility, symmetry energy, slope parameter and curvature of a neutron star are investigated using the relativistic energy density functional within the framework of coherent density fluctuation model. The analytical expression for the energy density functional of the neutron star matter is motivated from the Br $u ¨$ ckner functional and acquired by the polynomial fitting of the saturation curves for three different relativistic mean-field parameter sets (NL3, G3 and IU-FSU). The modified functional is folded with the neutron star's density-dependent weight function to calculate the numerical values for incompressibility and symmetry energy using the coherent density fluctuation model. NL3 parameter set, being the stiffest equation of state, endue us with a higher magnitude of all the properties compared to the other two parameter sets.
Comments:
9 pages, 3 figures, 2 tables. Matched with the published version. Published in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2105.07721 [pdf]
PRC(2021)·11 citations
08
[Submitted on 17 May 2021]
The drip lines of kaonic nuclei
J. Guo🇨🇳 · D. H. Chen🇨🇳 · Xian-Rong Zhou🇨🇳 · Q. B. Chen🇨🇳 · H.-J. Schulze🇮🇹
The effects of an additional $K^{-}$ meson on the neutron and proton drip lines are investigated within Skyrme-Hartree-Fock approach combined with a Skyrme-type kaon-nucleon interaction. While an extension of the proton drip line is observed due to the strongly attractive $K^{-} p$ interaction, contrasting effects (extension and reduction) on the neutron drip line of Be, O, and Ne isotopes are found. The origin of these differences is attributed to the behavior of the highest-occupied neutron single-particle levels near the neutron drip line.
Comments:
6 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2105.07735 [pdf]
0 citations
09
[Submitted on 17 May 2021]
Shell-model description for the first-forbidden $β^{-}$ decay of $^{207}$ Hg into the one-proton-hole nucleus $^{207}$ Tl
Anil Kumar🇮🇳 · Praveen C. Srivastava🇮🇳
In this work, we have performed large-scale shell-model calculations for the first-forbidden $β^{-}$ decay of $^{207}$ Hg into the one-proton-hole nucleus $^{207}$ Tl corresponding to the recently available experimental data from ISOLDE-CERN [T. A. Berry et al., Phys. Rev. C 101, 054311 (2020)]. We have used the one-particle one-hole ( $1 p$ - $1 h$ ) truncation for both protons and neutrons simultaneously across the doubly-shell closure at $^{208}$ Pb in the final states of $^{207}$ Tl. In our calculations, we have also considered the effect of mesonic enhancement $ϵ_{mec} = 2.01 \pm 0.05$ in the rank-0 for the axial-charge matrix element $γ_{5}$ . Here, we have calculated the $lo g f t$ values from the ground-state of $^{207}$ Hg to the several excited states of $^{207}$ Tl and obtained a good agreement between the calculated and the experimental data. In the experimental data spin and parity for some states are not yet confirmed, thus based on the shell-model results for the $lo g f t$ values we have given the prediction for these states. This is the first theoretical calculation for the $lo g f t$ values for these transitions.
Comments:
16 pages, 2 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.07781 [pdf]
NPA(2021)·14 citations
10
[Submitted on 17 May 2021]
Azimuthal dependence of two-particle transverse momentum current correlations
Niseem Magdy🇺🇸 · Sumit Basu🇸🇪 · Victor Gonzalez🇺🇸 · Ana Marin🇩🇪 · Olga Evdokimov🇺🇸 · Roy A. Lacey🇺🇸 · Claude Pruneau🇺🇸
Two-particle transverse momentum correlation functions are a powerful technique for understanding the dynamics of relativistic heavy-ion collisions. Among these, the transverse momentum correlator $G_{2} (Δ η, Δ φ)$ is of particular interest for its potential sensitivity to the shear viscosity per unit of entropy density $η / s$ of the quark-gluon plasma formed in heavy-ion collisions. We use the UrQMD, AMPT, and EPOS models for Au--Au at $s_{NN}$ = 200~GeV and Pb--Pb at $s_{NN}$ = 2760~GeV to investigate the long range azimuthal dependence of $G_{2} (Δ η, Δ φ)$ , and explore its utility to constrain $η / s$ based on charged particle correlations. We find that the three models yield quantitatively distinct transverse momentum Fourier harmonics coefficients $a_{n}^{p_{T}}$ . We also observe these coefficients exhibit a significant dependence on $η / s$ in the context of the AMPT model. These observations suggest that exhaustive measurements of the dependence of $G_{2} (Δ φ)$ with collision energy, system size, collision centrality, in particular, offer the potential to distinguish between different theoretical models and their underlying assumptions. Exhaustive analyses of $G_{2} (Δ φ)$ obtained in large and small systems should also be instrumental in establishing new constraints for precise extraction of $η / s$ .
Comments:
9 pages, 5 figures, submitted for publication
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2105.07912 [pdf]
EPJC(2021)·3 citations
11
[Submitted on 14 May 2021] (cross-list from astro-ph.HE)
Constraints on the dense matter equation of state and neutron star properties from NICER's mass-radius estimate of PSR J0740+6620 and multimessenger observations
G. Raaijmakers · S. K. Greif · K. Hebeler · T. Hinderer · S. Nissanke · A. Schwenk · T. E. Riley · A. L. Watts · J. M. Lattimer · W. C. G. Ho
In recent years our understanding of the dense matter equation of state (EOS) of neutron stars has significantly improved by analyzing multimessenger data from radio/X-ray pulsars, gravitational wave events, and from nuclear physics constraints. Here we study the additional impact on the EOS from the jointly estimated mass and radius of PSR J0740+6620, presented in Riley et al. (2021) by analyzing a combined dataset from X-ray telescopes NICER and XMM-Newton. We employ two different high-density EOS parameterizations: a piecewise-polytropic (PP) model and a model based on the speed of sound in a neutron star (CS). At nuclear densities these are connected to microscopic calculations of neutron matter based on chiral effective field theory interactions. In addition to the new NICER data for this heavy neutron star, we separately study constraints from the radio timing mass measurement of PSR J0740+6620, the gravitational wave events of binary neutron stars GW190425 and GW170817, and for the latter the associated kilonova AT2017gfo. By combining all these, and the NICER mass-radius estimate of PSR J0030+0451 we find the radius of a 1.4 solar mass neutron star to be constrained to the 95% credible ranges 12.33^{+0.76}_{-0.81} km (PP model) and 12.18^{+0.56}_{-0.79} km (CS model). In addition, we explore different chiral effective field theory calculations and show that the new NICER results provide tight constraints for the pressure of neutron star matter at around twice saturation density, which shows the power of these observations to constrain dense matter interactions at intermediate densities.
Comments:
17 pages, 8 figures; accepted for publication in the Astrophysical Journal Letters
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2105.06981 [pdf]
ApJL(2021)·454 citations
12
[Submitted on 15 May 2021] (cross-list from hep-ph)
Delta baryon photoproduction with twisted photons
Andrei Afanasev🇺🇸 · Carl E. Carlson🇺🇸
A future gamma factory at CERN or accelerator-based gamma sources elsewhere can include the possibility of energetic twisted photons, which are photons with a structured wave front that can allow a pre-defined large angular momentum along the beam direction. Twisted photons are potentially a new tool in hadronic physics, and we consider here one possibility, namely the photoproduction of $Δ$ (1232) baryons using twisted photons. We show that particular polarization amplitudes isolate the smaller partial wave amplitudes and they are measurable without interference from the terms that are otherwise dominant.
Comments:
9 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2105.07271 [pdf]
Annalen Phys.(2022)·14 citations
13
[Submitted on 16 May 2021] (cross-list from cond-mat.quant-gas)
Bose-Einstein condensation and non-extensive statistics
E. Megias🇪🇸 · V. S. Timóteo🇧🇷 · A. Gammal🇧🇷 · A. Deppman🇧🇷
We study the Bose-Einstein condensation in non-extensive statistics for a free gas of bosons, and extend the results to the non-relativistic case as well. We present results for the dependence of the critical temperature and the condensate fraction on the entropic index, q, and show that the condensate can exist only for a limited range of q in both relativistic and non-relativistic systems. We provide numerical results for other thermodynamics quantities like the internal energy, specific heat and number fluctuations. We discuss the implications for high energy physics and hadron physics. The results for the non-relativistic case can be of interest in cold-atom systems.
Comments:
18 pages, 11 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2105.07548 [pdf]
Physica A: Statistical Mechanics and its Applications(2022)·4 citations
14
[Submitted on 14 May 2021] (cross-list from physics.plasm-ph)
Current-Conserving Relativistic Linear Response for Collisional Plasmas
Martin Formanek🇺🇸 · Christopher Grayson🇺🇸 · Johann Rafelski🇺🇸 · Berndt Müller🇺🇸
We investigate the response of a relativistic plasma to electromagnetic fields in the framework of the Boltzmann equation incorporating a collision term in the relaxation rate approximation selected in a form assuring current conservation. We obtain an explicit solution for the linearized perturbation of the Fermi-Dirac equilibrium distribution in terms of the average relaxation rate $κ$ . We study the resulting covariant, gauge invariant, and current conserving form of the polarization tensor in the ultrarelativistic and non-relativistic limits. We evaluate the susceptibility in the ultrarelativistic limit and explore their dependence on $κ$ . Finally, we study the dispersion relations for the longitudinal and transverse poles of the propagator. We show that for $κ > 2 ω_{p}$ , where $ω_{p}$ is the plasma frequency, the plasma wave modes are overdamped. In the opposite case, $κ ≪ ω_{p}$ , the propagating plasma modes are weakly damped.
Comments:
14 pages, 9 figures
Subjects:
Plasma Physics (physics.plasm-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2105.07897 [pdf]
Annals Phys.(2021)·15 citations
15
[Submitted on 17 May 2021] (cross-list from hep-ph)
QED radiative corrections for accelerator neutrinos
Oleksandr Tomalak🇺🇸 · Qing Chen🇺🇸 · Richard J. Hill🇺🇸 · Kevin S. McFarland🇺🇸
Neutrino oscillation experiments at accelerator energies aim to establish charge-parity violation in the neutrino sector by measuring the energy-dependent rate of $ν_{e}$ appearance and $ν_{μ}$ disappearance in a $ν_{μ}$ beam. These experiments can precisely measure $ν_{μ}$ cross sections at near detectors, but $ν_{e}$ cross sections are poorly constrained and require theoretical inputs. In particular, quantum electrodynamics radiative corrections are different for electrons and muons. These corrections are proportional to the small quantum electrodynamics coupling $α \approx 1/137$ ; however, the large separation of scales between the neutrino energy and the proton mass ( $\sim GeV$ ), and the electron mass and soft-photon detection thresholds ( $\sim MeV$ ) introduces large logarithms in the perturbative expansion. The resulting flavor differences exceed the percent-level experimental precision and depend on nonperturbative hadronic structure. We establish a factorization theorem for exclusive charged-current (anti)neutrino scattering cross sections representing them as a product of two factors. The first factor is flavor universal; it depends on hadronic and nuclear structure and can be constrained by high-statistics $ν_{μ}$ data. The second factor is non-universal and contains logarithmic enhancements, but can be calculated exactly in perturbation theory. For charged-current elastic scattering, we demonstrate the cancellation of uncertainties in the predicted ratio of $ν_{e}$ and $ν_{μ}$ cross sections. We point out the potential impact of non-collinear energetic photons and the distortion of the visible lepton spectra and provide precise predictions for inclusive observables.
Comments:
8 pages, 5 figures, 1 table; v4: version published in Nature Communications, table 1 corrected, details of factorization and supplementary files added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2105.07939 [pdf]
Nature Commun.(2022)·45 citations

Affiliations

first authorsco-authorsvia INSPIRE