Nuclear Theory·nucl-th

Thursday·September 3, 2020

16 papers—9 primary·7 cross-listed

01
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.
nucl-thnucl-exPRC(2021)·17 citations
02
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.
nucl-thComput.Phys.Commun.(2021)·49 citations
03
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.
nucl-thnucl-exPTEP(2021)·17 citations
04
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.
nucl-thnucl-exResults Phys.(2021)·5 citations
05
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.
nucl-thPRC(2020)·13 citations
06
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.
nucl-thnucl-exPramana(2014)·0 citations
07
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.
nucl-thPRC(2021)·6 citations
08
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.
nucl-th1 citation
09
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.
nucl-thEPJA(2021)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE