Nuclear Theory·nucl-th

Thursday·March 22, 2018

14 papers—9 primary·5 cross-listed

01
Towards observation of three-nucleon short-range correlations in high Q^2 A(e, e')X reactions
Donal B. Day Leonid L. Frankfurt · Misak M. Sargsian · Mark I. Strikman
We present a detailed study of kinematical and dynamical conditions necessary for probing highly elusive three-nucleon short range correlations~(3N-SRCs) in nuclei through inclusive electron scattering. The kinematic requirements that should be satisfied in order to isolate 3N-SRCs in inclusive processes are derived. We demonstrate that a sequence of two short-range NN interactions represents the main mechanism for 3N-SRCs in inclusive processes. Within this mechanism we predict a quadratic dependence of the inclusive cross section ratios of nuclei to $^{3}$ He in the 3N-SRC region to the same ratio measured in 2N-SRC domain. The extended analysis of the available data satisfying the necessary 3N-SRC kinematical conditions is presented. This analysis provides tantalizing signatures of scaling associated with the onset of 3N-SRC dominance. The same data are also consistent with the prediction of the quadratic relation between the ratios measured in the 3N and 2N-SRC regions for nuclei ranging $4 \leq A \leq 197$ . This agreement made it possible to extract $a_{3} (A)$ , the probability of 3N-SRCs relative to the A=3 nucleus. We find $a_{3} (A)$ to be significantly larger in magnitude than the analogous parameter, $a_{2} (A)$ , for 2N-SRCs.
nucl-thhep-exhep-phnucl-exPRC(2023)·17 citations
02
The puzzling two-proton decay of $^{67}$ Kr
S.M. Wang · W. Nazarewicz
Two-proton (2 $p$ ) radioactivity is a rare decay mode found in a few proton-unbound nuclei. The $2 p$ -decay lifetime and properties of emitted protons carry invaluable information on nuclear structure in the presence of low-lying proton continuum. The recently measured $2 p$ decay of $^{67}$ Kr [Phys. Rev. Lett. 117, 162501 (2016)] turned out to be unexpectedly fast. Since $^{67}$ Kr is expected to be a deformed system, we investigate the impact of deformation effects on the $2 p$ radioactivity. We apply the recently developed Gamow coupled-channel framework, which allows for a precise description of three-body systems in the presence of rotational and vibrational couplings. This is the first application of a three-body approach to a two-nucleon decay from a deformed nucleus. We show that deformation couplings significantly increase the $2 p$ decay width of $^{67}$ Kr; this finding explains the puzzling experimental data. The calculated angular proton-proton correlations reflect a competition between $1 p$ and $2 p$ decay modes in this nucleus.
nucl-thPRL(2018)·58 citations
03
Prolate-to-oblate shape phase transitions in neutron-rich odd-mass nuclei
K. Nomura · R. Rodríguez-Guzmán · L. M. Robledo
We investigate the prolate-to-oblate shape phase transitions in the neutron-rich Pt, Os and Ir nuclei in the mass $A \approx 190$ region. The Hamiltonian of the interacting boson-fermion model, used to describe the odd-mass $^{185 - 199}$ Pt, $^{185 - 193}$ Os and $^{185 - 195}$ Ir isotopes, is partially constructed by using as a microscopic input the results of constrained self-consistent mean-field calculations within the Hartree-Fock-Bogoliubov method with the Gogny force. The remaining few parameters are adjusted to experimental data in the odd systems. In this way the calculations reasonably describe the spectroscopic properties of the odd-mass systems considered. Several calculated observables for the odd-mass nuclei, especially the low-energy excitation spectra and the effective deformation parameters, point to a prolate-oblate shape transition as a function of the neutron number for all the isotopic chains considered and similar to the one already observed in the neighboring even-even systems.
nucl-thnucl-exPRC(2018)·17 citations
04
Microscopic description of triaxiality in Ru isotopes with covariant energy density functional theory
Z. Shi · Z. P. Li
The triaxiality in nuclear low-lying states has attracted great interests for many years. Recently, the reduced transition probabilities for levels near the ground state in $^{110}$ Ru have been measured and provided strong evidences for a triaxial shape of this nucleus. The aim of this work is to provide a microscopic study of low-lying states for the Ru isotopes with $A \sim 100$ and to examine in detail the role of triaxiality, and the evolution of quadrupole shapes with the isospin and spin degrees of freedom. The low-lying excitation spectra and transition probabilities of even-even Ru isotopes are described at the beyond mean-field level by solving a five-dimensional collective Hamiltonian with parameters determined by constrained self-consistent mean-field calculations based on the relativistic energy density functional PC-PK1. The calculated energy surfaces, low-energy spectra, intraband and interband transition rates, as well as some characteristic collective observables, such as $E (4_{g.s.}^{+}) / E (2_{g.s.}^{+})$ , $E (2_{γ}^{+}) / E (4_{g.s.}^{+})$ , $B (E 2; 2_{g.s.}^{+} \to 0_{g.s.}^{+})$ , and $γ$ band staggerings are in a good agreement with the available experimental data. The main features of the experimental low-lying excitation spectra and electric transition rates are well reproduced, and thus strongly support the onset of triaxiality in the low-lying excited states of the Ru isotopes around $^{110}$ Ru.
nucl-thnucl-exPRC(2018)·21 citations
05
Analyses of multi-pion Hanbury-Brown-Twiss correlations for the pion-emitting sources with Bose-Einstein condensation
Ghulam Bary🇨🇳 · Peng Ru🇨🇳 · Wei-Ning Zhang🇨🇳
We calculate the three- and four-particle correlations of identical pions in an evolving pion gas (EPG) model with Bose-Einstein condensation. The multi-pion correlation functions in the EPG model are analyzed in different momentum intervals and compared with the experimental data for Pb-Pb collisions at $s_{N N} = 2.76$ TeV. It is found that the multi-pion correlation functions and cumulant correlation functions are sensitive to the condensation fraction of the EPG sources in the low average transverse-momentum intervals of the three and four pions. The model results of the multi-pion correlations are consistent with the experimental data in a considerable degree, which gives a source condensation fraction between 16~--~47\%.
nucl-thJ.Phys.G(2018)·16 citations
06
Mean free path and shear viscosity in central $^{129}$ Xe+ $^{119}$ Sn collisions below 100 MeV/nucleon
H. L. Liu🇨🇳 · Y. G. Ma🇨🇳 · A. Bonasera🇺🇸 · X. G. Deng🇨🇳 · O. Lopez🇫🇷 · M. Veselský🇸🇰
Thermal and transport properties of hot nuclear matter formed in central $^{129}$ Xe + $^{119}$ Sn collisions at the Fermi energy are investigated using the isospin-dependent quantum molecular dynamical (IQMD) model. Temperature ( $T$ ), average density ( $ρ$ ), chemical potential ( $μ$ ), mean momentum ( $P$ ), shear viscosity ( $η$ ) and entropy density ( $s$ ) are obtained from the phase-space information. The mean free path ( $λ_{nn}$ ) and the in-medium nucleon-nucleon cross section ( $σ_{nn}$ ) in the highest compressible stage at different incident energies are deduced and compared with the experimental results from Phys. Rev. C $90$ (2014) 064602. The result shows that $λ_{nn}$ and $σ_{nn}$ have the same trend and similar values as the experimental results when the beam energy is greater than 40 MeV/u at maximum compressed state. Furthermore, the derived shear viscosity over entropy density ( $η / s$ ) shows a decreasing behaviour to a saturated value around $\frac{3}{4 π}$ as a function of incident energy.
nucl-thnucl-exPRC(2017)·18 citations
07
Long-wavelength phonons in the crystalline and pasta phases of neutron-star crusts
David Durel🇫🇷 · Michael Urban🇫🇷
We study the long-wavelength excitations of the inner crust of neutron stars, considering three phases: cubic crystal at low densities, rods and plates near the core-crust transition. To describe the phonons, we write an effective Lagrangian density in terms of the coarse-grained phase of the neutron superfluid gap and of the average displacement field of the clusters. The kinetic energy, including the entrainment of the neutron gas by the clusters, is obtained within a superfluid hydrodynamics approach. The potential energy is determined from a model where clusters and neutron gas are considered in phase coexistence, augmented by the elasticity of the lattice due to Coulomb and surface effects. All three phases show strong anisotropy, i.e., angle dependence of the phonon velocities. Consequences for the specific heat at low temperature are discussed.
nucl-thastro-ph.HEPRC(2018)·19 citations
08
Photonuclear reaction as a probe for $α$ -clustering nuclei in the quasi-deuteron region
B. S. Huang · Y. G. Ma · W. B. He
Photon-nuclear reaction in a transport model frame, namely an Extended Quantum Molecular Dynamics (EQMD) model, has been realised at the photon energy of 70-140 MeV in the quasi-deuteron (QD) regime. For an important application, we pay a special focus on photonuclear reactions of $^{12}$ C( $γ$ ,np) $^{10}$ B where $^{12}$ C is considered as different configurations including $α$ -clustering. Obvious differences for some observables have been observed among different configurations, which can be attributed to spatial-momentum correlation of a neutron-proton pair inside nucleus, and therefore it gives us a sensitive probe to distinguish the different configurations including $α$ clustering with the help of the photonuclear reaction mechanism.
nucl-thnucl-exPRC(2017)·41 citations
09
Collective flows of $^{16}$ O + $^{16}$ O collisions with $α$ -clustering configurations
Chen-Chen Guo · Wan-Bing He · Yu-Gang Ma
The main purpose of the present paper is to discuss whether or not the collective flows in heavy-ion collision at Fermi energy can be taken as a tool to investigate the cluster configuration in light nuclei. In practice, within an Extended Quantum Molecular Dynamics model, four $α$ -clustering (linear chain, kite, square, and tetrahedron) configurations of $^{16}$ O are employed in the initialization, $^{16}$ O+ $^{16}$ O around Fermi energy (40 - 60 MeV $/$ nucleon) with impact parameter 1 - 3 fm are simulated, the directed and elliptic flows are analyzed. It is found that collective flows are influenced by the different $α$ -clustering configurations, and the directed flow of free protons is more sensitive to the initial cluster configuration than the elliptic flow. Nuclear reaction at Fermi energy can be taken a useful way to study cluster configuration in light nuclei.
nucl-thnucl-exChin.Phys.Lett.(2017)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE