Nuclear Theory·nucl-th

Thursday·June 4, 2020

8 papers—6 primary·2 cross-listed

01
Properties of neutron star described by a relativistic $ab ini t i o$ model
Chencan Wang🇨🇳 · Jinniu Hu🇨🇳 · Ying Zhang · Hong Shen🇨🇳
Properties of neutron star are investigated by an available relativistic $ab ini t i o$ method, i.e., the relativistic Brueckner-Hartree-Fock (RBHF) model, with the latest high-precision relativistic charge-dependent potentials, pvCD-Bonn A, B, C. The neutron star matter is solved within the beta equilibrium and charge neutrality conditions in the framework of RBHF model. Comparing to the conventional treatment, where the chemical potential of lepton was approximately represented by the symmetry energy of nuclear matter, the equation of state (EOS) of neutron star matter in the present self-consistent calculation with pvCD-Bonn B has striking difference above the baryon number density $n_{b} = 0.55$ fm $^{- 3}$ . However, these differences influence the global properties of neutron star only about $1% \sim 2%$ . Then, three two-body potentials pvCD-Bonn A, B, C, with different tensor components, are systematically applied in RBHF model to calculate the properties of neutron star. It is found that the maximum masses of neutron star are around $2.21 \sim 2.30 M_{⊙}$ and the corresponding radii are $R = 11.18 \sim 11.72$ km. The radii of $1.4 M_{⊙}$ neutron star are predicated as $R_{1.4} = 12.34 \sim 12.91$ km and their dimensionless tidal deformabilities are $Λ_{1.4} = 485 \sim 626$ . Furthermore, the direct URCA process in neutron star cooling will happen from $n_{b} = 0.414 \sim 0.530$ fm $^{- 3}$ with the proton fractions, $Y_{p} = 0.136 \sim 0.138$ . All of the results obtained from RBHF model only with two-body pvCD-Bonn potentials completely satisfy various constraints from recent astronomical observations of massive neutron stars, gravitational wave detection (GW 170817), and mass-radius simultaneous measurement (NICER).
nucl-thastro-ph.HEApJ(2020)·18 citations
02
Extended parity doublet model with a new transport code
Myungkuk Kim🇰🇷 · Sangyong Jeon🇨🇦 · Young-Min Kim🇰🇷 · Youngman Kim🇰🇷 · Chang-Hwan Lee🇰🇷
A new transport code "DaeJeon Boltzmann-Uehling-Uhlenbeck (DJBUU)" had been developed and enables to describe the dynamics of heavy-ion collisions in low-energy region. To confirm the validity of the new code, we first calculate Au + Au collisions at Ebeam = 100 and 400A MeV and also perform the box calculation to check the detail of collisions and Pauli blocking without mean-field potential as suggested by the Transport Code Comparison Project. After confirming the validity of new transport code, we study low-energy heavy-ion collisions with an extended parity doublet model. Since the distinctive feature of the parity doublet model is the existence of the chiral invariant mass that contributes to the nucleon mass, we investigate how physical quantities depend on the chiral invariant mass in heavy ion collisions at low energies. For this, we calculate physical quantities such as the effective nucleon mass in central collisions and transverse flow in semi-central collisions of Au + Au at Ebeam = 400A MeV with different values of the chiral invariant masses.
nucl-thPRC(2020)·13 citations
03
Sizes and shapes of very heavy nuclei in high-K states
M. Palczewski · P. Jachimowicz · M. Kowal
We have investigated shapes and sizes of selected two- and four-quasiparticle \mbox{high- $K$ } states in nobelium and rutherfordium isotopes within the microscopic-macroscopic model with the deformed Woods-Saxon potential. Excited nuclear configurations were obtained by blocking single-particle states lying close to the Fermi level. Their energies and deformations were found by the four-dimensional energy minimization over shape variables. We have selected the most promising candidates for \mbox{ $K$ -isomers} by analyzing the isotopic dependence of excitation energies, and compared our results to available experimental data. We calculated differences in quadrupole moments and charge radii between nuclei in their \mbox{high- $K$ } and ground states and found their quite different pattern for four-quasiparticle states in neighboring No and Rf isotopes. The leading role of the quadrupole and hexadecapole deformations as well as the importance of higher rank symmetries are also discussed. The current development of laser techniques and the resulting ability to measure discussed effects in the near future is the motivation of our study.
nucl-th1 citation
04
Strangeness production and hypernuclear formation in proton and antiproton induced reactions
Zhao-Qing Feng🇨🇳
Strange particles and hyperfragments in collisions of antiprotons and protons on nuclei have been investigated systematically within a microscopic transport model. The hyperons are produced from the annihilation in antibaryon-baryon collisions and strangeness exchange process in antiproton induced reactions. A coalescence approach is used for constructing the primary hyperfragments in phase space and the statistical model is modified for describing the decay of hyperfragments via evaporating hyperon, neutron, charged particles etc, in which the shell effect, binding energy and root-mean-square radii are taken into account. It is found that the influence of the hyperon-nucleon interaction on the free $Λ$ and $Ξ^{-}$ production is negligible. However, the large hyperfragment yields are obvious with the attractive potential. The production of double strangeness hyperfragments are reduced below 1 $μ b$ in comparison to the yields of $Λ$ -hyperfragments with the cross sections of 0.05-0.1 mb in the antiproton induced reactions on $^{63}$ Cu at the incident momenta of 1-5 GeV/c. The light hyperfragments are formed in the dynamical fragmentation process. The energy dependence of hyperfragment formation is weak once the incident energy above the threshold energy for the hyperon production.
nucl-thPRC(2020)·7 citations
05
Production mechanism of neutron-deficient actinide isotopes in complete fusion reactions and multinucleon transfer reactions
Peng-Hui Chen · Fei Niu · Zhao-Qing Feng
Within the dinuclear system model, unknown neutron-deficient isotopes Np, Pu, Am, Cm, Bk, Cf, Es, Fm are investigated in $^{40}$ Ca, $^{36, 40}$ Ar, $^{32}$ S, $^{28}$ Si, $^{24}$ Mg induced fusion-evaporation reactions and multinucleon transfer reactions with radioactive beams $^{59}$ Cu, $^{69}$ As, $^{90}$ Nb, $^{91}$ Tc, $^{94}$ Rh, $^{105, 110}$ Sn, $^{118}$ Xe induced with $^{238}$ U near Coulomb barrier energies. The production cross sections of compound nuclei in the fusion-evaporation reactions and fragments yields in the multinucleon transfer reactions are calculated within the model. A statistical approach is used to evaluate the survival probability of excited nuclei via the both reaction mechanisms. A dynamical deformation is implemented into the model in the dissipation process. It is found that charge particle channels (alpha and proton) dominate in the decay process of proton-rich nuclides and the fusion-evaporation reactions are favorable to produce the new neutron-deficient actinide isotopes. The total kinetic energies and angular spectra of primary fragments are strongly dependent on colliding orientations.
nucl-thPRC(2020)·4 citations
06
Pre-hydrodynamic evolution and its signatures in final-state heavy-ion observables
Tiago Nunes da Silva🇧🇷 · David Chinellato🇧🇷 · Mauricio Hippert🇧🇷 · Willian Serenone🇧🇷 · Jun Takahashi🇧🇷 · Gabriel S. Denicol🇧🇷 · Matthew Luzum🇧🇷 · Jorge Noronha🇺🇸
We investigate the effects of pre-hydrodynamic evolution on final-state observables in heavy-ion collisions using state-of-the art event simulations coupled to different pre-hydrodynamic scenarios, which include the recently-developed effective kinetic transport theory evolution model KoMPoST. Flow observables are found to be insensitive to the details of pre-hydrodynamic evolution. The main effect we observe is in the $p_{T}$ spectra, particularly the mean transverse momentum. However, at least part of this effect is a consequence of the underlying conformal invariance assumption currently present in such approaches, which is known to be violated in the temperature regime probed in heavy-ion collisions. This assumption of early time conformal invariance leads to an artificially large out-of-equilibrium bulk pressure when switching from (conformal) pre-hydrodynamic evolution to hydrodynamics (using the non-conformal QCD equation of state), which in turn increases the transverse momentum. Our study indicates that a consistent treatment of pre-hydrodynamic evolution in heavy-ion collisions requires the use of non-conformal models of early time dynamics.
nucl-thhep-phnucl-exPRC(2021)·45 citations
07
On the minimum radius of very massive neutron stars
Sophia Han🇺🇸 · Madappa Prakash🇺🇸
Prospects of establishing the radii of massive neutron stars in PSR J1614-2230 and PSR J0740+6620 from NICER and Chandra observatories hold the potential to constrain the equation of state (EoS) of matter to densities well beyond those encountered in canonical stars of mass $\sim 1.4 M_{⊙}$ . In this work, we investigate the relation between the radii of very massive neutron stars up to the maximum mass, $M_{max}$ , supported by dense matter EoSs. Results from models with hadronic matter are contrasted with those that include a first-order hadron-to-quark phase transition. We find that a lower bound on $M_{max}$ with an upper bound on the radius of massive pulsars serves to rule out too soft quark matter, and an upper bound on $M_{max}$ with a lower bound on the radius of massive pulsars strongly disfavors a transition into too-stiff quark matter appearing at low densities. The complementary role played by radius inferences from future gravitational wave events of inspiraling binary neutron stars is also briefly discussed.
↳ astro-ph.HEastro-ph.SRnucl-thApJ(2020)·56 citations
08
Pion observables calculated in Minkowski and Euclidean spaces with Ansätze for quark propagators
Dalibor Kekez🇭🇷 · Dubravko Klabučar🇭🇷
We study two quark--propagator meromorphic Ansätze that admit clear connection between calculations in Euclidean space and Minkowski spacetime. The connection is established through a modified Wick rotation in momentum space, where the integration contour along the imaginary axis is adequately deformed. The Ansätze were previously proposed in the literature and fitted to Euclidean lattice QCD data. The generalized impulse approximation is used to calculate the pion transition form factor and electromagnetic form factor, correcting an earlier result. The pion decay constant and distribution amplitude are also calculated. The latter is used to deduce the asymptotic behavior of the form factors. Such an asymptotic behavior is compared with those obtained directly from the generalized impulse approximation and the causes of differences are pointed out.
↳ hep-phnucl-thPRD(2023)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE