Nuclear Theory·nucl-th

Friday·February 16, 2018

9 papers—5 primary·4 cross-listed

01
Single-particle potential of the $Λ$ hyperon in nuclear matter with chiral effective field theory NLO interactions including effects of YNN three-baryon interactions
M. Kohno🇯🇵
Adopting hyperon-nucleon and hyperon-nucleon-nucleon interactions parametrized in chiral effective field theory, single-particle potentials of the $Λ$ and $Σ$ hyperons are evaluated in symmetric nuclear matter and in pure neutron matter within the framework of lowest order Bruckner theory. The chiral NLO interaction bears strong $Λ$ N- $Σ$ N coupling. Although the $Λ$ potential is repulsive if the coupling is switched off, the $Λ$ N- $Σ$ N correlation brings about the attraction consistent with empirical data. The $Σ$ potential is repulsive, which is also consistent with empirical information. The interesting result is that the $Λ$ potential becomes shallower beyond normal density. This provides the possibility to solve the hyperon puzzle without introducing ad hoc assumptions. The effects of the $Λ$ NN- $Λ$ NN and $Λ$ NN- $Σ$ NN three-baryon forces are considered. These three-baryon forces are first reduced to normal-ordered effective two-baryon interactions in nuclear matter and then incorporated in the $G$ -matrix equation. The repulsion from the $Λ$ NN- $Λ$ NN interaction is of the order of 5 MeV at the normal density, and becomes larger with increasing the density. The effects of the $Λ$ NN- $Σ$ NN coupling compensate the repulsion at normal density. The net effect of the three-baryon interactions to the $Λ$ single-particle potential is repulsive at higher densities.
nucl-thPRC(2018)·32 citations
02
Beta - and gamma-decay transition rates in the two-group shell model
V.I. Isakov
In the framework of the two-group configuration model we obtain formulas for the reduced transition rates for beta- and gamma-transitions in even-even, odd-odd, even-odd, and odd-even nuclei. We explored dependencies of the transition rates on the occupancies of the involved subshells, as well as on the spin values of the initial and final states. The obtained formulas are useful for the qualitative spectroscopic analysis of experimental data, particulary in the regions of magicity, including the regions of the "remote" nuclei.
nucl-th0 citations
03
Neutron star equation of state from the quark level in the light of GW170817
Zhen-Yu Zhu🇨🇳 · En-Ping Zhou🇨🇳 · Ang Li🇨🇳
Matter state inside neutron stars is an exciting problem in astrophysics, nuclear physics and particle physics. The equation of state (EOS) of neutron stars plays a crucial role in the present multimessenger astronomy, especially after the event of GW170817. We propose a new neutron star EOS "QMF18" from the quark level, which describes well robust observational constraints from free-space nucleon, nuclear matter saturation, heavy pulsar measurements and the tidal deformability of the very recent GW170817 observation. For this purpose, we employ the quark-mean-field (QMF) model, allowing one to tune the density dependence of the symmetry energy and study effectively its correlations with the Love number and the tidal deformability. We provide tabulated data for the new EOS and compare it with other recent EOSs from various many-body frameworks.
nucl-thastro-ph.HEastro-ph.SRApJ(2018)·107 citations
04
Charge Symmetry Breaking Effects in Pion and Kaon Structure
Parada T. P. Hutauruk🇰🇷 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸 · Anthony W. Thomas🇦🇺
Charge symmetry breaking (CSB) effects associated with the $u$ and $d$ quark mass difference are investigated in the quark distribution functions and spacelike electromagnetic form factors of the pion and kaon. We use a confining version of the Nambu--Jona-Lasinio model, where CSB effects at the infrared scale associated with the model are driven by the dressed $u$ and $d$ quark mass ratio, which because of dynamical chiral symmetry breaking is much closer to unity than the associated current quark mass ratio. The pion and kaon are given as bound states of a dressed quark and a dressed antiquark governed by the Bethe-Salpeter equation, and exhibit the properties of Goldstone bosons, with a pion mass difference given by $m_{π^{+}}^{2} - m_{π^{0}}^{2} \propto (m_{u} - m_{d})^{2}$ as demanded by dynamical chiral symmetry breaking. We find significant CSB effects for realistic current quark mass ratios ( $m_{u} / m_{d} \sim 0.5$ ) in the quark flavor-sector electromagnetic form factors of both the pion and kaon. For example, the difference between the $u$ and $d$ quark contributions to the $π^{+}$ electromagnetic form factors is about 8\% at a momentum transfer of $Q^{2} ≃ 10$ GeV $^{2}$ , while the analogous effect for the light quark sector form factors in the $K^{+}$ and $K^{0}$ is about twice as large. For the Parton distribution functions, we find CSB effects which are considerably smaller than those found in the electromagnetic form factors.
nucl-thhep-phPRC(2018)·31 citations
05
Quantal Diffusion Description of Multi-Nucleon Transfers in Heavy-Ion Collisions
S. Ayik · B. Yilmaz · O. Yilmaz · A. S. Umar
Employing the stochastic mean-field (SMF) approach, we develop a quantal diffusion description of the multi-nucleon transfer in heavy-ion collisions at finite impact parameters. The quantal transport coefficients are determined by the occupied single-particle wave functions of the time-dependent Hartree-Fock equations. As a result, the primary fragment mass and charge distribution functions are determined entirely in terms of the mean-field properties. This powerful description does not involve any adjustable parameter, includes the effects of shell structure and is consistent with the fluctuation-dissipation theorem of the non-equilibrium statistical mechanics. As a first application of the approach, we analyze the fragment mass distribution in $^{48} Ca +^{238} U$ collisions at the bombarding energy $E_{c.m.} = 193$ MeV and compare the calculations with the experimental data.
nucl-thPRC(2018)·62 citations

Affiliations

first authorsco-authorsvia INSPIRE

Single-particle potential of the Λ hyperon in nuclear matter with chiral effective field theory NLO interactions including effects of YNN three-baryon interactions

Beta - and gamma-decay transition rates in the two-group shell model

Neutron star equation of state from the quark level in the light of GW170817

Charge Symmetry Breaking Effects in Pion and Kaon Structure

Quantal Diffusion Description of Multi-Nucleon Transfers in Heavy-Ion Collisions

Affiliations

Single-particle potential of the $Λ$ hyperon in nuclear matter with chiral effective field theory NLO interactions including effects of YNN three-baryon interactions