Nuclear Theory·nucl-th

Friday·December 4, 2020

19 papers—9 primary·10 cross-listed

01
[Submitted on 2 Dec 2020]
Intrinsic Correlations Among Characteristics of Neutron-rich Matter Imposed by the Unbound Nature of Pure Neutron Matter
Bao-Jun Cai · Bao-An Li
The unbound nature of pure neutron matter (PNM) requires intrinsic correlations between the symmetric nuclear matter (SNM) EOS parameters (incompressibility $K_{0}$ , skewness $J_{0}$ and kurtosis $I_{0}$ ) and those (slope $L$ , curvature $K_{sym}$ and skewness $J_{sym}$ ) characterizing the symmetry energy independent of any nuclear many-body theory. We investigate these intrinsic correlations and their applications in better constraining the poorly known high-density behavior of nuclear symmetry energy. Several novel correlations connecting the characteristics of SNM EOS with those of nuclear symmetry energy are found. In particular, at the lowest-order of approximations, the bulk parts of the slope $L$ , curvature $K_{sym}$ and skewness $J_{sym}$ of the symmetry energy are found to be $L \approx K_{0} /3, K_{sym} \approx L J_{0} /2 K_{0}$ and $J_{sym} \approx I_{0} L /3 K_{0}$ , respectively. High-order corrections to these simple relations can be written in terms of the small ratios of high-order EOS parameters. The resulting intrinsic correlations among some of the EOS parameters reproduce very nicely their relations predicted by various microscopic nuclear many-body theories and phenomenological models constrained by available data of terrestrial experiments and astrophysical observations in the literature. The unbound nature of PNM is fundamental and the required intrinsic correlations among the EOS parameters characterizing both the SNM EOS and symmetry energy are universal. These intrinsic correlations provide a novel and model-independent tool not only for consistency checks but also for investigating the poorly known high-density properties of neutron-rich matter by using those with smaller uncertainties.
Comments:
Phys. Rev. C in press
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
2012.01549 [pdf]
PRC(2021)·10 citations
02
[Submitted on 3 Dec 2020]
The evolution of magnetic dipole strength in $^{100 - 140}$ Sn isotope chain and quenching of nucleon g factors
G. Kruzic · T. Oishi · N. Paar
The evolution of electromagnetic transitions along isotope chains is of particular importance for the nuclear structure and dynamics, as well as for the r-process nucleosynthesis. Recent measurement of inelastic proton scattering on even-even $^{112 - 124}$ Sn isotopes provides a novel insight into the isotopic dependence of E1 and M1 strength distributions. We investigate M1 transitions in even-even $^{100 - 140}$ Sn isotopes from a theoretical perspective, based on relativistic nuclear energy density functional. The M1 transition strength distribution is characterized by an interplay between single and double-peak structures, that can be understood from the evolution of single-particle states, their occupations governed by the pairing correlations, and two-quasiparticle transitions involved. It is shown that discrepancy between model calculations and experiment on B(M1) transition strength is considerably reduced than previously known, and the quenching of the g-factors for the free nucleons needed to reproduce the experimental data on M1 transition strength amounts $g_{e f f} / g_{f r ee}$ =0.80-0.93. Since some of the B(M1) strength above the neutron threshold may be missing in the inelastic proton scattering measurement, further experimental studies are required to confirm if only small modifications of the bare g-factors are actually needed when applied in finite nuclei.
Comments:
8 pages, 7 figures, revised version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2012.01622 [pdf]
PRC(2021)·9 citations
03
[Submitted on 3 Dec 2020]
Empirical formalism for the production of neutron-rich nuclei using fragmentation of medium heavy neutron-rich Rare Isotope Beam
Debasis Bhowmick · Siddhartha Dechoudhury · Vaishali Naik · Alok Chakrabarti
We report here an empirical formalism for predicting the cross-sections of neutron-rich nuclei produced in fragmentation of relativistic \b{eta}-unstable neutron-rich projectiles in the mid-mass region. The formalism is based on the abrasion-ablation picture of the projectile fragmentation reaction. It has been shown that the formalism can accurately reproduce the experimental cross-section data for nuclei produced in the fragmentation of 132Sn. The formalism, it is shown, can also reproduce the experimental cross-sections of neutron-rich nuclei produced in the fragmentation of 129Xe fairly accurately. The formalism is used to bring out the advantage in the production cross-sections of neutron-rich isotopes, especially the more neutron-rich ones; that one can expect by using unstable doubly magic neutron-rich projectile 132Sn as compared to comparatively less neutron-rich unstable projectile 128Sn and also 124Sn, the isotope which is most neutron-rich among the stable isotopes of Sn (tin). The formalism is used to predict the cross-sections of neutron-rich nuclei produced in the fragmentation reaction of unstable 144Xe and 146Cs, which are expected to be produced with sufficient intensity in the upcoming RIB facilities and in the existing RIB facilities after beam intensity upgrade.
Comments:
5 figures, 3 Tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.01702 [pdf]
0 citations
04
[Submitted on 3 Dec 2020]
Finite particle number description of neutron matter using the unitary correlation operator and high-momentum pair methods
Niu Wan · Takayuki Myo · Chang Xu · Hiroshi Toki · Hisashi Horiuchi · Mengjiao Lyu
By using bare Argonne V4' (AV4'), V6' (AV6'), and V8' (AV8') nucleon-nucleon (NN) interactions respectively, the nuclear equations of state (EOSs) for neutron matter are calculated with the unitary correlation operator and high-momentum pair methods. The neutron matter is described under a finite particle number approach with magic number $N = 66$ under a periodic boundary condition. The central short-range correlation coming from the short-range repulsion in the NN interaction is treated by the unitary correlation operator method (UCOM) and the tensor correlation and spin-orbit effects are described by the two-particle two-hole (2p2h) excitations of nucleon pairs, in which the two nucleons with a large relative momentum are regarded as a high-momentum pair (HM). With the 2p2h configurations increasing, the total energy per particle of neutron matter is well converged under this UCOM+HM framework. By comparing the results calculated with AV4', AV6', and AV8' NN interactions, the effects of the short-range correlation, the tensor correlation, and the spin-orbit coupling on the density dependence of the total energy per particle of neutron matter are demonstrated. Moreover, the contribution of each Hamiltonian component to the total energy per particle is discussed. The EOSs of neutron matter calculated within the present UCOM+HM framework agree with the calculations of six different microscopic many-body theories, especially in agreement with the auxiliary field diffusion Monte Carlo calculations.
Comments:
13 pages, 6 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.01790 [pdf]
CPC(2020)·6 citations
05
[Submitted on 3 Dec 2020]
Multiple Dirac eikonal scattering of polarized intermediate-energy protons by nuclei
V. V. Pilipenko · V. I. Kuprikov (National Science Center Kharkov Institute of Physics and Technology)
An improved model of the multiple Dirac eikonal scattering of proton on nucleons of the target nucleus is considered. In this model, the amplitudes of elastic $p - A$ scattering are found on the basis of the Watson series of multiple scattering by means of the eikonal expansion of the Dirac propagator for the free proton motion between scattering events on nucleons, and the nucleus structure is described in the relativistic mean field model. The calculations have been performed for the complete set of observables for the elastic $p +^{40}$ Ca and $p +^{208}$ Pb scattering at 800 MeV. The effects of allowing for distinction between the relativistic scalar and vector nucleon densities on the description of the $p - A$ scattering observables have been studied, as well as the results of calculations using nucleon densities obtained in different modern variants of the relativistic mean field model have been compared.
Comments:
15 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.01893 [pdf]
0 citations
06
[Submitted on 3 Dec 2020]
Three-nucleon force contribution to the deuteron channel in $(d, p)$ reactions
N.K. Timofeyuk · M.J. Dinmore · J.S AL-Khalili
The contribution of a three-nucleon (3N) force, acting between the neutron and proton in the incoming deuteron with a target nucleon, to the deuteron-target potential in the entrance channel of the $A (d, p) B$ reaction has been calculated within the adiabatic distorted wave approximation (ADWA). Four different 3N interaction sets from local chiral effective field theory ( $χ$ EFT) at next-to-next-to-leading order (N2LO) were used. Strong sensitivity of the adiabatic deuteron-target potential to the choice of the 3N force format has been found, which originates from the enhanced sensitivity to the short-range physics of nucleon-nucleon (NN) and 3N interactions in the ADWA. Such a sensitivity is reduced when a Watanabe folding model is used to generate $d$ - $A$ potential instead of ADWA. The impact of the 3N force contribution on $(d, p)$ cross sections depends on assumptions made about the $p$ - $A$ and $n$ - $A$ optical potentials used to calculate the distorted $d$ - $A$ potential in the entrance channel. It is different for local and nonlocal optical potentials and depends on whether the induced three-body force arising due to neglect of target excitations is included or not.
Comments:
Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.01996 [pdf]
0 citations
07
[Submitted on 3 Dec 2020]
Fluctuations of anisotropic flow from the finite number of rescatterings in a two-dimensional massless transport model
Hendrik Roch🇩🇪 · Nicolas Borghini🇩🇪
We investigate the fluctuations of anisotropic transverse flow due to the finite number of scatterings in a two-dimensional system of massless particles. Using a set of initial geometries from a Monte Carlo Glauber model, we study how flow coefficients fluctuate about their mean value at the corresponding eccentricity, for several values of the scattering cross section. We also show how the distributions of the second and third event planes of anisotropic flow about the corresponding participant plane in the initial geometry evolve as a function of the mean number of scatterings in the system.
Comments:
v2: final version, 17 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2012.02138 [pdf]
EPJC(2021)·18 citations
08
[Submitted on 3 Dec 2020]
Constraining the nonanalytic terms in the isospin-asymmetry expansion of the nuclear equation of state
Pengsheng Wen · Jeremy W. Holt
We examine the properties of the isospin-asymmetry expansion of the nuclear equation of state from chiral two- and three-body forces. We focus on extracting the high-order symmetry energy coefficients that consist of both normal terms (occurring with even powers of the isospin asymmetry) as well as terms involving the logarithm of the isospin asymmetry that are formally nonanalytic around the expansion point of isospin-symmetric nuclear matter. These coefficients are extracted from numerically precise perturbation theory calculations of the equation of state coupled with a new set of finite difference formulas that achieve stability by explicitly removing the effects of higher-order terms in the expansion. We consider contributions to the symmetry energy coefficients from both two- and three-body interactions. It is found that the coefficients of the logarithmic terms are generically larger in magnitude than those of the normal terms from second-order perturbation theory diagrams, but overall the normal terms give larger contributions to the ground state energy. The high-order isospin-asymmetry terms are especially relevant at large densities where they affect the proton fraction in beta-equilibrium matter.
Comments:
12 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.02163 [pdf]
PRC(2021)·23 citations
09
[Submitted on 3 Dec 2020]
Constraining the initial stages of ultrarelativistic nuclear collisions
Jakub Jankowski🇵🇱 · Syo Kamata🇵🇱 · Mauricio Martinez🇺🇸 · Michał Spaliński🇵🇱
It is frequently supposed that quark-gluon plasma created in heavy-ion collisions undergoes free streaming at early times. We examine this issue based on the assumption that a universal attractor dominates the dynamics already at the earliest stages, which offers a way to connect the initial state with the start of the hydrodynamic expansion in an approximate but conceptually transparent fashion. We demonstrate that the centrality dependence of the measured particle multiplicities can be used to quantitatively constrain the pressure anisotropy and find that it strongly depends on the model of the initial energy deposition. As an illustration, we compare three initial state models and show that they predict rather different early-time values of the pressure anisotropy. This strongly suggests that assuming free streaming prior to hydrodynamization is not necessarily compatible with a generic initial state model and that features of the pre-hydrodynamic flow need to be matched with the model of the initial state.
Comments:
v2: significantly extended; v3: presentation improved
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2012.02184 [pdf]
PRD(2021)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE