Nuclear Theory·nucl-th

Thursday·September 3, 2020

16 papers—9 primary·7 cross-listed

01
[Submitted on 1 Sept 2020]
Microscopic investigation of the $^{8}$ Li( $n, γ$ ) $^{9}$ Li reaction
Callum McCracken🇨🇦 · Petr Navratil🇨🇦 · Anna McCoy🇨🇦 · Sofia Quaglioni🇺🇸 · Guillaume Hupin🇫🇷
The $^{8}$ Li( $n, γ$ ) $^{9}$ Li reaction plays an important role in several astrophysics scenarios. It cannot be measured directly and indirect experiments have so far provided only cross section limits. Theoretical predictions differ by an order of magnitude. In this work we study the properties of $^{9}$ Li bound states and low-lying resonances and calculate the $^{8}$ Li( $n, γ$ ) $^{9}$ Li cross section within the no-core shell model with continuum (NCSMC) with chiral nucleon-nucleon and three-nucleon interactions as the only input. The NCSMC is an ab initio method applicable to light nuclei that provides a unified description of bound and scattering states well suited to calculate low-energy nuclear scattering and reactions. Our calculations reproduce the experimentally known bound states as well as the lowest $5/ 2^{-}$ resonance of $^{9}$ Li. We predict a $3/ 2^{-}$ spin-parity assignment for the resonance observed at 5.38 MeV. In addition to the a very narrow $7/ 2^{-}$ resonance corresponding presumably to the experimental 6.43 MeV state, we find several other broad low-lying resonances. Our calculated $^{8}$ Li( $n, γ$ ) $^{9}$ Li cross section is within the limits derived from the 1998 National Superconducting Cyclotron Laboratory Coulomb-dissociation experiment [Phys. Rev. C {\bf 57}, 959 (1998)]. However, it is higher than cross sections obtained in recent phenomenological studies. It is dominated by a direct E1 capture to the ground state with a resonant contribution at $\sim 0.2$ MeV due to E2/M1 radiation enhanced by the $5/ 2^{-}$ resonance.
Comments:
12 pages, 9 figures, version accepted for publication
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2009.00658 [pdf]
PRC(2021)·17 citations
02
[Submitted on 1 Sept 2020]
The LISE package: solvers for static and time-dependent superfluid local density approximation equations in three dimensions
Shi Jin · Kenneth J. Roche · Ionel Stetcu · Ibrahim Abdurrahman · Aurel Bulgac
Nuclear implementation of the density functional theory (DFT) is at present the only microscopic framework applicable to the whole nuclear landscape. The extension of DFT to superfluid systems in the spirit of the Kohn-Sham approach, the superfluid local density approximation (SLDA) and its extension to time-dependent situations, time-dependent superfluid local density approximation (TDSLDA), have been extensively used to describe various static and dynamical problems in nuclear physics, neutron star crust, and cold atom systems. In this paper, we present the codes that solve the static and time-dependent SLDA equations in three-dimensional coordinate space without any symmetry restriction. These codes are fully parallelized with the message passing interface (MPI) library and take advantage of graphic processing units (GPU) for accelerating execution. The dynamic codes have checkpoint/restart capabilities and for initial conditions one can use any generalized Slater determinant type of wave function. The code can describe a large number of physical problems: nuclear fission, collisions of heavy ions, the interaction of quantized vortices with nuclei in the nuclear star crust, excitation of superfluid fermion systems by time dependent external fields, quantum shock waves, domain wall generation and propagation, the dynamics of the Anderson-Bogoliubov-Higgs mode, dynamics of fragmented condensates, vortex rings dynamics, generation and dynamics of quantized vortices, their crossing and recombinations and the incipient phases of quantum turbulence.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.00745 [pdf]
Comput.Phys.Commun.(2021)·49 citations
03
[Submitted on 2 Sept 2020]
The mean square radius of the neutron distribution and the skin thickness derived from electron scattering
Haruki Kurasawa · Toshimi Suda · Toshio Suzuki
The second-order moment of the nuclear charge density( $R_{c}^{2}$ ) is dominated by the mean square radius(msr) of the point proton distribution( $R_{p}^{2}$ ), while the fourth-order moment( $Q_{c}^{4}$ ) depends on the msr of the point neutron one( $R_{n}^{2}$ ) also. Moreover, $R_{n}^{2}$ is strongly correlated to $R_{c}^{2}$ in nuclear models. According to these facts, the linear relationship between various moments in the nuclear mean field models are investigated with use of the least squares method for $^{40}$ Ca, $^{48}$ Ca and $^{208}$ Pb. From the intersection points of the obtained straight lines with those of the experimental values for $R_{c}^{2}$ and $Q_{c}^{4}$ determined through electron scattering, the values of $R_{p}$ and $R_{n}$ are estimated. Since relativistic and non-relativistic models provide different lines, the obtained values of $R_{n}$ and the skin thickness( $R_{n} - R_{p}$ ) differ from each other in the two frameworks.
Comments:
39 pages and 28 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2009.00759 [pdf]
PTEP(2021)·17 citations
04
[Submitted on 2 Sept 2020]
Reanalyses for $^{42 - 51}$ Ca scattering on a $^{12}$ C target at $280$ MeV/nucleon based on chiral $g$ folding mode with Gogny-D1S Hartree-Fock-Bogoliubov densities (published in Results in Physics)
Maya Takechi · Tomotsugu Wakasa · Shingo Tagami Jun Matsui · Masanobu Yahiro
In the previous paper, we predicted reaction cross sections $σ_{R}$ for $^{40 - 60, 62, 64}$ Ca+ $^{12}$ C scattering at $280$ ~MeV/nucleon, since Tanaka {\it el al.} measured interaction cross sections $σ_{I}$ for $^{42 - 51}$ Ca in RIKEN and determined neutron skin $r_{skin} (RIKEN)$ using the optical limit of the Glauber model with the Woos-Saxon densities. Our purpose is to reanalyze the $r_{skin}$ from the $σ_{I}$ . Our analysis is superior to theirs, since the chiral $g$ -matrix folding model (the GHFB and GHFB+AMP densities) is much better than the optical limit of the Glauber model (the Woos-Saxon densities). Our model is the chiral $g$ -matrix folding model with the densities scaled from the GHFB and GHFB+AMP densities. We scale the GHFB and GHFB+AMP densities so that the $σ_{R}$ of the scaled densities can agree with the central values of $σ_{I}$ under the condition that the proton radius of the scaled proton density equals the data determined from the isotope shift based on the electron scattering. The $r_{skin}$ thus determined are close to their results $r_{skin}^{42 - 51} (RIKEN)$ . For $^{48}$ Ca, our value $r_{skin}^{48}$ is 0.105 $\pm$ 0.06~fm, while their value is $r_{m}^{48} (RIKEN) = 0.146 \pm 0.06$ ~fm. We take the weighted mean and its error of $r_{skin}^{48} (σ_{I}) = 0.105 \pm 0.06$ ~fm and $r_{skin}^{48} (E 1 pE) = 0.17 \pm 0.03$ ~fm of the high-resolution $E 1$ polarizability experiment (E1{\rm pE}). Our final result is $r_{skin}^{48} = 0.157 \pm 0.027$ ~fm. Our conclusion is $r_{skin}^{48} = 0.157 \pm 0.027$ ~fm for $^{48}$ Ca. For $^{42 - 47, 49 - 51}$ Ca, our results on $r_{skin}$ are similar to theirs. Our result for $^{48}$ Ca is related to CREX.
Comments:
6 pages, 3 figure
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2009.00796 [pdf]
Results Phys.(2021)·5 citations
05
[Submitted on 2 Sept 2020]
Bridging the quartet and pair pictures of isovector proton-neutron pairing
V.V. Baran🇷🇴 · D. R. Nichita🇷🇴 · D. Negrea🇷🇴 · D. S. Delion🇷🇴 · N. Sandulescu🇷🇴 · P. Schuck🇫🇷
The formal implications of a quartet coherent state ansatz for proton-neutron pairing are analyzed. Its nonlinear annihilation operators, which generalize the BCS linear quasiparticle operators, are computed in the quartetting case. Their structure is found to generate nontrivial relationships between the many body correlation functions. The intrinsic structure of the quartet coherent state is detailed, as it hints to the precise correspondence between the quartetting picture and the symmetry restored pair condensate picture for the proton-neutron pairing correlations.
Comments:
6 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.00932 [pdf]
PRC(2020)·13 citations
06
[Submitted on 1 Sept 2020]
Nuclear Multifragmentation: Basic Concepts
G. Chaudhuri · S. Mallik · S. Das Gupta
We present a brief overview of nuclear multifragmentation reaction. Basic formalism of canonical thermodynamical model based on equilibrium statistical mechanics is described. This model is used to calculate basic observables of nuclear multifragmentation like mass distribution, fragment multiplicity, isotopic distribution and isoscaling. Extension of canonical thermodynamical model to a projectile fragmentation model is outlined. Application of the projectile fragmentation model for calculating average number of intermediate mass fragments and the average size of largest cluster at different $Z_{b o u n d}$ , differential charge distribution and cross-section of neutron rich nuclei of different projectile fragmentation reactions at different energies are described. Application of nuclear multifragmentation reaction in basic research as well as in other domains is outlined.
Comments:
Proceedings of the National Conference on Nuclear Physics 2013, Sambalpur University, Sambalpur, India. arXiv admin note: text overlap with arXiv:1209.0281
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2009.00985 [pdf]
Pramana(2014)·0 citations
07
[Submitted on 2 Sept 2020]
Role of continuum in nuclear direct reactions with one-neutron halo nuclei: a one-dimensional model
Laura Moschini · Antonio M. Moro · Andrea Vitturi
We study the evolution of a single-particle wave function during the collision of a one dimensional potential well by another well, which can be regarded as a simple model for the problem of the scattering of a one-neutron halo nucleus by another nucleus. This constitutes an effective three-body problem, whose solution in three dimensions can be extremely complicated, particularly when breakup and rearrangement channels are to be considered. Our one-dimensional model provides the essential three-body nature of this problem, and allows for a much simpler application and assessment of different methods of solution. To simplify further the problem, we assume that the potential well representing the projectile moves according to a predetermined classical trajectory, although the internal motion of the "valence" particle is treated fully quantum-mechanically. This corresponds to a semiclassical approach of the scattering problem. Different approaches are investigated to understand the dynamics involving one-body halo-like systems: the "exact" time-dependent solution of the Schrödinger equation is compared to a numerical continuum-discretized coupled-channels (CC) calculation presenting various model cases including different reaction channels. This framework allows us to discuss the reaction mechanism and the role of continuum, whose inclusion in the CC calculation results to be crucial to reproduce the "exact" solution, even when the initial and final states are well bound. We also link each dynamical situation with analogous problem solved in a three dimensional (3D) CC framework, discussing the main challenges experienced in the usual 3D models.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.01159 [pdf]
PRC(2021)·6 citations
08
[Submitted on 2 Sept 2020]
Real-time measurements of solar $pp$ neutrinos using $^{131}$ Xe
J. Kostensalo🇫🇮 · J. Suhonen🇫🇮 · K. Zuber🇩🇪
Various large-scale experiments for double beta decay or dark matter are based on xenon. Current experiments are on the tonne scale but there are also ideas to aim for even larger sizes in the future. Here we study the potential of the isotope $^{131}$ Xe to allow to make real-time measurements of solar $pp$ neutrinos, besides classical neutrino-electron scattering. Improved nuclear models are used to determine the cross-section of neutrinos on $^{131}$ Xe. The present calculations deviate significantly from the previous ones due to updated estimates for the excited-state contributions. The updated capture-rate estimate for $pp$ neutrinos is $(4.47 \pm 0.09) SNU$ and for all solar neutrinos $(80 \pm 21) SNU$ , with neutrino survival probabilities taken into account. Depending on the amount of Xe, solar $pp$ neutrinos might be measured with rates of 100 per day, thus allowing to monitor them in real time for a long period.
Comments:
7 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.01164 [pdf]
1 citation
09
[Submitted on 2 Sept 2020]
Finite-temperature mean-field approximations for shell model Hamiltonians: the code HF-SHELL
W. Ryssens · Y. Alhassid
We present the code HF-SHELL for solving the self-consistent mean-field equations for configuration-interaction shell model Hamiltonians in the proton-neutron formalism. The code can calculate both ground-state and finite-temperature properties in the Hartree-Fock (HF), HF+Bardeen-Cooper-Schrieffer (HF+BCS), and the Hartree-Fock-Bogoliubov (HFB) mean-field approximations. Particle-number projection after variation is incorporated to reduce the grand-canonical ensemble to the canonical ensemble, making the code particularly suitable for the calculation of nuclear state densities. The code does not impose axial symmetry and allows for triaxial quadrupole deformations. The self-consistency cycle is particularly robust through the use of the heavy-ball optimization technique and the implementation of different options to constrain the quadrupole degrees of freedom.
Comments:
18 pages, 5 figures, source code repository can be found at http://github.com/wryssens/hf-shell
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.01205 [pdf]
EPJA(2021)·12 citations
10
[Submitted on 30 Aug 2020] (cross-list from hep-ph)
Enhancement of low-mass dileptons in ultraperipheral collisions
I.M. Dremin🇷🇺 · S.R. Gevorkyan🇷🇺 · D.T. Madigozhin🇷🇺
It is shown that production of low-mass $e^{+} e^{-}$ -pairs in ultraperipheral nuclear collisions is enhanced due to the Sommerfeld-Gamow-Sakharov (SGS) factor. This effect is especially strong near the threshold of creation of unbound $e^{+} e^{-}$ -pairs with low masses in the two-photon fusion. Coulomb attraction of the non-relativistic components of such pairs may lead to the increased intensity of 511 keV photons. It can be recorded at the NICA collider and has some astrophysical implications. The analogous effect can be observed at LHC in dilepton production.
Comments:
10 p., 3 Figs
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2008.13184 [pdf]
EPJC(2021)·8 citations
11
[Submitted on 2 Sept 2020] (cross-list from hep-th)
Covariant propagator and chiral power counting
Zhou Liu🇨🇳 · Li-Hong Wen🇨🇳 · J.-F. Yang🇨🇳
Some one-loop diagrams with one and two external baryons/nucleons are revisited using covariant baryon propagators in chiral effective theory. We showed that it is enough to separate and subtract all the local terms that violate chiral power counting to recover chiral power counting, no need to introduce extra operations. The structures of leading chiral corrections and IR enhancement or threshold effects are 'stable' or persist as long as covariant propagators are employed for all particles.
Comments:
9 pages, 11 figures, final version, accepted for publication in Nuclear Physics B
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2009.00753 [pdf]
NPB(2021)·2 citations
12
[Submitted on 2 Sept 2020] (cross-list from nucl-ex)
Estimation of CP violating EDMs from known mechanisms in the SM
Prajwal Mohanmurthy🇺🇸 · Jeff A. Winger🇺🇸
New sources of CP violation, beyond the known sources in the standard model (SM), are required to explain the baryon asymmetry of the universe. Measurement of a non-zero permanent electric dipole moment (EDM) for fundamental particles, such as in an electron or a neutron, or in nuclei or atoms, can help us gain a handle on the sources of CP violation, both in SM and beyond. Multiple mechanisms within the SM can generate CP violating EDMs, viz.\ through the CKM matrix in the weak sector or through the QCD $θ ˉ$ parameter in the strong sector. We will estimate the maximum possible EDMs of leptons, certain baryons, select atoms and molecules in the (CKM $⨁ θ ˉ$ ) framework, assuming that the EDM wholly originates from either of the two SM mechanisms, independently. These estimates have been presented in light of the current experimental upper limits on the EDMs, in the following systems - leptons: $e^{-}$ , $μ^{-}$ , $τ^{-}$ , $ν_{e}^{0}$ , $ν_{μ}^{0}$ , $ν_{τ}^{0}$ , baryons: $n^{0}$ , $p^{+}$ , $Λ^{0}$ , $Σ^{0}$ , $Ξ^{0}$ , $Λ_{c}^{+}$ , $Ξ_{c}^{+}$ , atoms: $^{85}$ Rb, $^{133}$ Cs, $^{210}$ Fr, $^{205}$ Tl, $^{199}$ Hg, $^{129}$ Xe, $^{225}$ Ra, $^{223}$ Rn, and molecules: HfF $^{+}$ , PbO, YbF, ThO, RaF, TlF. Particularly, to drive home the point that EDMs in different systems constrain CP-violating interactions differently, we show that the same measured constraint on the EDM in two different systems may not actually be equally constraining on CP violating parameters, and to emphasize the need to measure a non-zero EDM in multiple systems before understanding the origins of these CP-violating EDMs.
Comments:
Proceedings of The 40th International Conference on High Energy Physics, ICHEP-2020; Jul 28-Aug 6, 2020, Prague, Czech Republic; Abs. ID: 97. 11 Pages, 6 Tables, 1 figure. Version 1 sets ${C_{S}, C_{T}} = 0$ , these constraints have been relaxed in version 3. Version 2 experimental values (red) are expected measurement sensitivities in the near future. Typos have been edited
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.00852 [pdf]
PoS(2021)·4 citations
13
[Submitted on 2 Sept 2020] (cross-list from astro-ph.HE)
GW190814: Circumstantial Evidence for Up-Down Quark Star
Zheng Cao🇨🇳 · Lie-Wen Chen🇨🇳 · Peng-Cheng Chu🇨🇳 · Ying Zhou🇨🇳
Within a confining quark matter model which considers phenomenologically the quark confinement and asymptotic freedom as well as the chiral symmetry restoration and quark deconfinement at high baryon density, we find that if the up-down quark matter ( $u d$ QM) is more stable than nuclear matter and strange quark matter (SQM), the maximum mass of static quark stars with $u d$ QM is $2.87 M_{⊙}$ under agreement with both the constraints on star tidal deformability from gravitational wave signal GW170817 and the mass-radius of PSR J0030+0451 and PSR J0740+6620 measured by NICER. In contrast, the conventional strange quark star with the SQM that is more stable than nuclear matter while the nuclear matter is more stable than $u d$ QM, has a maximum static mass of only $1.87 M_{⊙}$ and its radius significantly deviates from NICER's constraint. Our results thus provide circumstantial evidence suggesting the recently reported GW190814's secondary component with a mass of $2.5 9_{- 0.09}^{+ 0.08} M_{⊙}$ could be an up-down quark star.
Comments:
6 pages, 2 figures. Results updated and discussions added. Accepted version to appear in PRD
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.00942 [pdf]
PRD(2022)·64 citations
14
[Submitted on 2 Sept 2020] (cross-list from hep-ph)
Holography in Quark-Gluon Plasma and Neutron Stars
Govert Nijs🇳🇱
In this thesis, QCD is studied from three different directions, with one overarching theme: holography. The holographic duality allows certain strongly coupled QFTs to be described in terms of much simpler classical gravity in one dimension more. The first direction from which QCD is studied in this thesis is by examining the effects of an external magnetic field on a particular holographic model of QCD, yielding interesting qualitative insight. The second approach examines how, in the same model, one can describe dense baryonic configurations, providing a new way to study the matter composing neutron stars. Indeed, the equation of state produced in this way is subsequently used to compute several neutron star properties which are observable, or will be in the near future. The last direction contains no holographic computations per se, but does incorporate several qualitative insights from holography into a new heavy ion code called Trajectum. This will in the near future be used to perform a Bayesian analysis, whereby it is hoped that these qualitative insights from holography can be tested on experimental data, to see how well the ideas coming from holography match up with experiment.
Comments:
PhD Thesis, 202 pages, 49 figures, http://dspace.library.uu.nl/handle/1874/397298
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2009.01138 [pdf]
1 citation
15
[Submitted on 2 Sept 2020] (cross-list from hep-ph)
Strange quark mass turns magnetic domain walls into multi-winding flux tubes
Geraint W. Evans🇬🇧 · Andreas Schmitt🇬🇧
Dense quark matter is expected to behave as a type-II superconductor at strong coupling. It was previously shown that if the strange quark mass $m_{s}$ is neglected, magnetic domain walls in the so-called 2SC phase are the energetically preferred magnetic defects in a certain parameter region. Computing the flux tube profiles and associated free energies within a Ginzburg-Landau approach, we find a cascade of multi-winding flux tubes as "remnants" of the domain wall when $m_{s}$ is increased. These flux tubes exhibit an unconventional ring-like structure of the magnetic field. We show that flux tubes with winding numbers larger than one survive for values of $m_{s}$ up to about 20% of the quark chemical potential. This makes them unlikely to play a significant role in compact stars, but they may appear in the QCD phase diagram in the presence of an external magnetic field.
Comments:
25 pages, 6 figures; v2: minor improvements, extended discussion on length scales of the flux tubes, to appear in J.Phys.G
Subjects:
High Energy Physics — Phenomenology (hep-ph); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)
arXiv:
2009.01141 [pdf]
J.Phys.G(2021)·5 citations
16
[Submitted on 2 Sept 2020] (cross-list from nucl-ex)
Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in $^{208}$ Pb
M. Spieker · A. Heusler · B. A. Brown · T. Faestermann · R. Hertenberger · G. Potel · M. Scheck · N. Tsoneva · M. Weinert · H.-F. Wirth · A. Zilges
New experimental data on the neutron single-particle character of the Pygmy Dipole Resonance (PDR) in $^{208}$ Pb are presented. They were obtained from $(d, p)$ and resonant proton scattering experiments performed at the Q3D spectrograph of the Maier-Leibnitz Laboratory in Garching, Germany. The new data are compared to the large suite of complementary, experimental data available for $^{208}$ Pb and establish $(d, p)$ as an additional, valuable, experimental probe to study the PDR and its collectivity. Besides the single-particle character of the states, different features of the strength distributions are discussed and compared to Large-Scale-Shell-Model (LSSM) and energy-density functional (EDF) plus Quasiparticle-Phonon Model (QPM) theoretical approaches to elucidate the microscopic structure of the PDR in $^{208}$ Pb.
Comments:
9 pages, 4 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2009.01151 [pdf]
PRL(2020)·30 citations

Affiliations

first authorsco-authorsvia INSPIRE