Nuclear Theory·nucl-th

Wednesday·June 30, 2021

10 papers—6 primary·4 cross-listed

01
Solving the puzzle of nuclear stopping power
Marek Jeżabek🇵🇱 · Andrzej Rybicki🇵🇱
This paper reviews our recent findings on the dynamics of transport of baryon number in proton-induced reactions at the CERN SPS. These are put in a more general context of the present understanding of baryon stopping phenomena up to LHC and cosmic ray energies. The implications of our studies, advantages to be provided by modern and high quality experimental data, and perspectives of new measurements are shortly discussed.
nucl-thhep-phActa Phys.Polon.B(2021)·4 citations
02
Ground-state properties of light $4 n$ self-conjugate nuclei in $ab$ $ini t i o$ no-core Monte Carlo shell model calculations with nonlocal $N N$ interactions
T. Abe · P. Maris · T. Otsuka · N. Shimizu · Y. Utsuno · J. P. Vary
We report $J^{π} = 0^{+}$ ground-state energies and point-proton radii of $^{4}$ He, $^{8}$ Be, $^{12}$ C, $^{16}$ O and $^{20}$ Ne nuclei calculated by the $ab$ $ini t i o$ no-core Monte Carlo shell model with the JISP16 and Daejeon16 nonlocal $N N$ interactions. Ground-state energies are obtained in the basis spaces up to seven oscillator shells ( $N_{shell} = 7$ ) with several oscillator energies ( $ℏ ω$ ) around the optimal oscillator energy for the convergence of ground-state energies. These energy eigenvalues are extrapolated to obtain estimates of converged ground state energies in each basis space using energy variances of computed energy eigenvalues. We further extrapolate these energy-variance-extrapolated energies obtained in the finite basis spaces to infinite basis-space results with an empirical exponential form. This form features a dependence on the basis-space size but is independent of the value of $ℏ ω$ used for the harmonic-oscillator basis functions. Point-proton radii for these states of atomic nuclei are also calculated following techniques employed for the energies. From these results, it is found that the Daejeon16 $N N$ interaction provides good agreement with experimental data up to approximately $^{16}$ O, while the JISP16 $N N$ interaction provides good agreement with experimental data up to approximately $^{12}$ C. Beyond these nuclei, the interactions produce overbinding accompanied by radii that are too small. These findings suggest and encourage further revisions of nonlocal $N N$ interactions towards the investigation of nuclear structure in heavier-mass regions.
nucl-thPRC(2021)·16 citations
03
Model selection for $K^{+} Σ^{-}$ photoproduction within isobar model
Petr Bydžovský🇨🇿 · Aleš Cieplý🇨🇿 · Dimitrios Petrellis🇨🇿 · Dalibor Skoupil🇨🇿 · Nicholas Zachariou🇬🇧
We utilise an isobar model to investigate the $K^{+} Σ^{-}$ photoproduction off a neutron in the resonance region. Except for the Born terms, we include high-spin (spin-3/2 and spin-5/2) nucleon resonances in the consistent formalism together with a few $Δ$ and kaon resonances to achieve an acceptable agreement with data. Interestingly, we reveal that no hyperon resonances are needed to achieve a reasonable description of data. On the other hand the $N (1720) 3/ 2^{+}$ resonance was found to be very important for correct description of data. The free parameters of the model were fitted to experimental data from the LEPS and CLAS Collaborations on either differential cross sections or photon beam asymmetry. The novel feature of the fitting procedure is the use of a regularization method, the Least Absolute Shrinkage Selection Operator, and information criteria in order to choose the best fit.
nucl-thPRC(2021)·16 citations
04
Negative R-parity scissors modes in the Two-Rotors Model
Fabrizio Palumbo
In a previous work I constructed R-negative scissors states in the Two-Rotors Model in which the rotors are two-sided classical bodies. Such states have |K| = 1; 0 components and negative space parity. Here I extend this work including reflections in a plane through the rotors symmetry axes obtaining also R-negative states of positive parity. I then associate reflections and R-operations with corresponding operations on internal noncollective variables of the rotors. I evaluate the em transition strengths of these states and compare them with the corresponding strengths of R-positive scissors modes.
nucl-th0 citations
05
Questioning the wobbling interpretation of low-spin bands in $γ$ -soft nuclei within the interacting boson-fermion model
K. Nomura🇭🇷 · C. M. Petrache🇫🇷
An alternative interpretation of the recently reported low-lying excited bands in $γ$ -soft odd-mass nuclei as wobbling bands is presented in terms of the interacting boson-fermion model. The model Hamiltonian is determined based on the mean-field calculations with the nuclear energy density functionals. The predicted mixing ratios of the $Δ I = 1$ electric quadrupole to magnetic dipole transition rates between yrast bands and those yrare bands previously interpreted as wobbling bands in $^{135}$ Pr, $^{133}$ La, $^{127}$ Xe, and $^{105}$ Pd are consistently smaller in magnitude than the experimental values on which the wobbling interpretation is based. These calculated mixing ratios indicate predominant magnetic character in agreement with the new experimental data. The earlier wobbling assignments are severely questioned.
nucl-thnucl-exPRC(2022)·17 citations
06
Fast & accurate emulation of two-body scattering observables without wave functions
J. A. Melendez🇺🇸 · C. Drischler🇺🇸 · A. J. Garcia🇺🇸 · R. J. Furnstahl🇺🇸 · Xilin Zhang🇺🇸
We combine Newton's variational method with ideas from eigenvector continuation to construct a fast & accurate emulator for two-body scattering observables. The emulator will facilitate the application of rigorous statistical methods for interactions that depend smoothly on a set of free parameters. Our approach begins with a trial $K$ or $T$ matrix constructed from a small number of exact solutions to the Lippmann--Schwinger equation. Subsequent emulation only requires operations on small matrices. We provide several applications to short-range potentials with and without the Coulomb interaction and partial-wave coupling. It is shown that the emulator can accurately extrapolate far from the support of the training data. When used to emulate the neutron-proton cross section with a modern chiral interaction as a function of 26 free parameters, it reproduces the exact calculation with negligible error and provides an over 300x improvement in CPU time.
nucl-thcond-mat.mtrl-scihep-lathep-ph+1PLB(2021)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE

Solving the puzzle of nuclear stopping power

Ground-state properties of light 4n self-conjugate nuclei in ab initio no-core Monte Carlo shell model calculations with nonlocal NN interactions

Model selection for K+Σ− photoproduction within isobar model

Negative R-parity scissors modes in the Two-Rotors Model

Questioning the wobbling interpretation of low-spin bands in γ-soft nuclei within the interacting boson-fermion model

Fast & accurate emulation of two-body scattering observables without wave functions

Affiliations

Ground-state properties of light $4 n$ self-conjugate nuclei in $ab$ $ini t i o$ no-core Monte Carlo shell model calculations with nonlocal $N N$ interactions

Model selection for $K^{+} Σ^{-}$ photoproduction within isobar model

Questioning the wobbling interpretation of low-spin bands in $γ$ -soft nuclei within the interacting boson-fermion model