Nuclear Theory·nucl-th

Monday·March 16, 2020

12 papers—6 primary·6 cross-listed

01
Signature dependent triaxiality for shape evolution from superdeformation in rapidly rotating $^{40}$ Ca and $^{41}$ Ca
Shinkuro Sakai · Kenichi Yoshida · Masayuki Matsuo
We investigate the possible occurrence of the highly-elongated shapes near the yrast line in $^{40}$ Ca and $^{41}$ Ca at high spins on the basis of the nuclear energy-density functional method. Not only the superdeformed (SD) yrast configuration but the yrare configurations on top of the SD band are described by solving the cranked Skyme-Kohn-Sham equation in the three-dimensional coordinate-space representation. It is suggested that some of the excited SD bands undergo band crossings and develop to the hyperdeformation (HD) beyond $J ≃ 25ℏ$ in $^{40}$ Ca. We find that the change of triaxiality in response to rotation plays a decisive role for the shape evolution towards HD, and that this is governed by the signature quantum number of the last occupied orbital at low spins. This mechanism can be verified in an experimental observation of the positive-parity SD yrast signature-partner bands in $^{41}$ Ca, one of which ( $α = + 1/2$ ) undergoes crossings with the HD band while the other ( $α = - 1/2$ ) shows the smooth evolution from the collective rotation at low spins to the non-collective rotation with oblate shape at the termination.
nucl-thnucl-exPTEP(2020)·10 citations
02
Study of nuclear matter properties for Hybrid EoS
I. A. Rather🇮🇳 · A. A. Usmani🇮🇳 · S. K. Patra🇮🇳
We study the nuclear matter properties like symmetry energy, slope parameter, curvature, skewness and incompressibility for Hybrid EoS. The hybrid EoS is constructed using the recently proposed Effective-Field-Theory motivated Relativistic Mean-Field model (E-RMF) for the hadron phase with different parameter sets and MIT Bag model for the quark phase with different Bag constants to construct hybrid EoS. The mixed-phase formed by the hadron-quark phase transition is studied using the Gibbs construction. The nuclear matter properties for hybrid EoS are calculated and their variation with the bag constant is determined.
nucl-thJ.Phys.G(2020)·4 citations
03
TDHF and a macroscopic aspect of low-energy nuclear reactions
Kouhei Washiyama · Kazuyuki Sekizawa
Time-dependent Hartree--Fock (TDHF) method has been applied to various low-energy nuclear reactions, such as fusion, fission, and multinucleon transfer reactions. In this Mini Review, we summarize recent attempts to bridge a microscopic nuclear reaction theory, TDHF, and a macroscopic aspect of nuclear reactions through nucleus--nucleus potentials and energy dissipation from macroscopic degrees of freedom to microscopic ones obtained from TDHF in various colliding systems from light to heavy mass regions.
nucl-thnucl-exFront.in Phys.(2020)·9 citations
04
Determination of symmetry energy from experimental and observational constraints; prediction on CREX
Shingo Tagami · Nobutoshi Yasutake · Mitsunori Fukuda · Jun Matsui · Masanobu Yahiro
Taking $r_{skin}^{208} (PREX) = 0.3 3_{- 0.18}^{+ 0.16} fm$ as an experimental constraint and $M_{max}^{NS} \geq 2 M_{sun}$ as an observational (astrophysical) constraint, we determine an indisputable range for $J$ , $L$ , $K_{sym}$ defined in Eq.~\eqref{eq-S-sym}. For this purpose, we take a statistical approach. We first accumulate the 206 EoS data from theoretical works and take correlation between $r_{skin}^{208}$ and $L$ for the 206 EoSs, where 7 Gogny EoSs are obtained by our calculations. Since the correlation coefficient is $R = 0.99$ , we can regard $L$ as a function of $r_{skin}^{208}$ , so that we succeed in deducing an empirical constraint $L = 31 - 161$ ~MeV from $r_{skin}^{208} (PREX) = 0.15 - 0.49$ ~fm. For the 47 EoSs satisfying the observational constraint, 46 EoSs satisfy the empirical constraint. The 46 EoSs yield $J = 29 - 44$ ~MeV, $L = 37 - 135$ ~MeV, $K_{sym} = (- 137) - (160)$ ~MeV. The is a primary result. When we take correlation between $r_{skin}^{48}$ and $r_{skin}^{208}$ for the 206 EoSs, $R$ is 0.99. The $r_{skin}^{48}$ -- $r_{skin}^{208}$ relation allows us to transform $r_{skin}^{208} (PREX)$ into the corresponding data on $r_{skin}^{48}$ In order to estimate a value of $r_{skin}^{48}$ for ongoing CREX, we take the weighted mean and its error of two present data on $r_{skin}^{48}$ and transformed PREX value on $r_{skin}^{48}$ . The weighted mean is $r_{skin}^{48} = 0.17$ ~fm. This is a prediction for the central value of CREX.
nucl-th8 citations
05
Uncertainty of three-nucleon continuum observables arising from uncertainties of two-nucleon potential parameters
Yu. Volkotrub · J. Golak · R. Skibiński · K. Topolnicki · H. Witała · E.Epelbaum · H. Krebs · P. Reinert
Propagation of uncertainties from two-nucleon potential parameters to three-nucleon observables, that is statistical errors for the neutron-deuteron elastic scattering and the deuteron breakup reaction at neutron laboratory energies up to 200 MeV is investigated. To that end we use the chiral nucleon-nucleon interaction with the semi-local momentum-space regularization at various orders of the chiral expansion, exploiting knowledge of the covariance matrix of its parameters. For both reactions we compare statistical uncertainties for chiral predictions with the uncertainties obtained in the same way but for the semi-phenomenological One-Pion-Exchange two-nucleon force. In addition for the elastic scattering we show also the truncation errors arising from restriction to a given order of chiral predictions, estimated among others within the Bayesian method, and the cutoff dependence of chiral predictions. We find that the resulting statistical uncertainty is smaller than the truncation errors for the chiral force at lower orders of the chiral expansion. At the higher orders of the chiral expansion and at low energies the statistical errors exceed the truncation ones but at intermediate and higher energies truncation errors are more important. Overall, magnitudes of the theoretical uncertainties are small and amount up to 0.5\%-4\%, depending on the observable and energy. We also find that the magnitudes of statistical uncertainties for the chiral and semi-phenomenological potentials are similar and that the dependence of predictions on the regularization parameter values is important at all investigated energies.
nucl-thJ.Phys.G(2020)·11 citations
06
Dispersion (asymptotic) theory of charged particle transfer reactions at low energies and nuclear astrophysics: I. the "non-dramatic" case
R. Yarmukhamedov · K. I. Tursunmakhatov
A new dispersion (asymptotic) theory is proposed for the peripheral sub- and above-barrier charged particle transfer $A (x, y) B$ reaction in the three-body ( $A$ , $a$ and $y$ ) model where $x = y + a$ and $B = A + a$ , and $a$ is a transferred particle. It is based on the combination of the dispersion theory and the conventional DWBA method. The explicit forms have been derived for the exact three-body pole amplitude and differential cross section in which the contribution of the three-body ( $A$ , $a$ and $y$ ) Coulomb dynamics of the transfer mechanism in the peripheral partial amplitudes, corresponding to partial waves with $l_{i} >> 1$ , is taken into account correctly. For the specific peripheral proton and triton transfer reactions, the comparative analysis of the peripheral partial amplitudes at $l_{i} >> 1$ , which correspond to the one-step pole and exact three-body pole amplitudes as well as those of the "post"-approximation and the post form of the conventional DWBA, is performed with each other. It shows the absolute inapplicability of the "post"-approximation usually applied for getting an information about specific asymptotic normalization coefficients being astrophysical interest.
nucl-th0 citations
07
Collins-Soper Kernel for TMD Evolution from Lattice QCD
Phiala Shanahan🇺🇸 · Michael Wagman🇺🇸 · Yong Zhao🇺🇸
The Collins-Soper kernel relates transverse momentum-dependent parton distribution functions (TMDPDFs) at different energy scales. For small parton transverse momentum $q_{T} \sim Λ_{QCD}$ , this kernel is non-perturbative and can only be determined with controlled uncertainties through experiment or first-principles calculations. This work presents the first exploratory determination of the Collins-Soper kernel using the lattice formulation of Quantum Chromodynamics. In a quenched calculation, the $N_{f} = 0$ kernel is determined at scales in the range 250 MeV $< q_{T} < 2$ GeV, and an analysis of the remaining systematic uncertainties is undertaken.
↳ hep-lathep-phnucl-thPRD(2020)·137 citations
08
Meson-baryon scattering in resummed baryon chiral perturbation theory using time-ordered perturbation theory
X.-L. Ren🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪
Integral equations for meson-baryon scattering amplitudes are obtained by utilizing time-ordered perturbation theory for a manifestly Lorentz-invariant formulation of baryon chiral perturbation theory. Effective potentials are defined as sums of two-particle irreducible contributions of time-ordered diagrams and the scattering amplitudes are obtained as solutions of integral equations. Ultraviolet renormalizability is achieved by solving integral equations for the leading order amplitude and including higher order corrections perturbatively. As an application of the developed formalism, pion-nucleon scattering is considered.
↳ hep-phnucl-thEPJC(2020)·8 citations
09
Momentum Anisotropy of Leptons from Two Photon Processes in Heavy Ion Collisions
Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸 · Jian Zhou🇨🇳
We investigate the azimuthal angular correlation between the lepton transverse momentum $P_{⊥}$ and the impact parameter $b_{⊥}$ in non-central heavy-ion collisions, where the leptons are produced through two-photon scattering. Among the Fourier harmonic coefficients, a significant $v_{4}$ asymmetry is found for the typical kinematics at RHIC and LHC with a mild dependence on the $P_{⊥}$ , whereas $v_{2}$ is power suppressed by the lepton mass over $P_{⊥}$ . This unique prediction, if confirmed from the experiments, shall provide crucial information on the production mechanism for the dilepton in two-photon processes.
↳ hep-phhep-exnucl-exnucl-thPRL(2020)·37 citations
10
Charge radius of the short-lived $^{68}$ Ni and correlation with the dipole polarizability
S. Kaufmann🇩🇪 · J. Simonis🇩🇪 · S. Bacca🇩🇪 · J. Billowes🇬🇧 · M. L. Bissell🇬🇧 · K. Blaum🇩🇪 · B. Cheal🇬🇧 · R. F. Garcia Ruiz🇬🇧 · W. Gins🇧🇪 · C. Gorges🇩🇪 · G. Hagen🇺🇸 · H. Heylen🇩🇪 and 17 other authors
We present the first laser spectroscopic measurement of the neutron-rich nucleus $^{68}$ Ni at the \mbox{ $N = 40$ } subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability $α_{D}$ has been measured, the combination of these observables provides a benchmark for nuclear structure theory. We compare them to novel coupled-cluster calculations based on different chiral two- and three-nucleon interactions, for which a strong correlation between the charge radius and dipole polarizability is observed, similar to the stable nucleus $^{48}$ Ca. Three-particle--three-hole correlations in coupled-cluster theory substantially improve the description of the experimental data, which allows to constrain the neutron radius and neutron skin of $^{68}$ Ni.
↳ nucl-exnucl-thPRL(2020)·48 citations
11
Spallation of r-Process Nuclei Ejected from a Neutron Star Merger
Xilu Wang · Brian D. Fields · Matthew Mumpower · Trevor Sprouse · Rebecca Surman · Nicole Vassh
Neutron star mergers (NSMs) are rapid neutron capture (r-process) nucleosynthesis sites, which eject materials at high velocities, from 0.1c to as high as 0.6c. Thus the r-process nuclei ejected from a NSM event are sufficiently energetic to initiate spallation reactions with the interstellar medium (ISM) particles. With a thick-target model for the propagation of high-speed heavy nuclei in the ISM, we find that spallation reactions may shift the r-process abundance patterns towards solar data, particularly around the low-mass edges of the r-process peaks where neighboring nuclei have very different abundances. The spallation effects depend both on the astrophysical conditions of the r-process nuclei and nuclear physics inputs for the nucleosynthesis calculations and the propagation process. This work extends that of [Wang et al.(2019)] by focusing on the influence of nuclear physics variations on spallation effects.
↳ astro-ph.HEnucl-thJ.Phys.Conf.Ser.(2020)·0 citations
12
Semiclassical Approximation meets Keldysh-Schwinger diagrammatic technique: Scalar $φ^{4}$
A.A. Radovskaya🇷🇺 · A.G. Semenov🇷🇺
We study the evolution of the non-equilibrium quantum fields from a highly excited initial state in two approaches: the standard Keldysh-Schwinger diagram technique and the semiclassical expansion. We demonstrate explicitly that these two approaches coincide if the coupling constant $g$ and the Plank constant $ℏ$ are small simultaneously. Also, we discuss loop diagrams of the perturbative approach, which are summed up by the leading order term of the semiclassical expansion. As an example, we consider shear viscosity for the scalar field theory at the leading semiclassical order. We introduce the new technique that unifies both semiclassical and diagrammatic approaches and open the possibility to perform the resummation of the semiclassical contributions.
↳ hep-phcond-mat.stat-mechhep-thnucl-thEPJC(2021)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE