The Effects Of Pion And Gluon Corrections On Nuclear Structure In The Quark Mean Field Model

In order to study the nuclear many-body system,in this thesis the corrections of the pion and gluon effects to the baryon mass based on the quark mean field（QMF）model are introduced.In the QMF model,the baryon consists of three constituent quarks con-fined by harmonic oscillator potentials.Due to the important roles of chiral symmetry and gluons in quantum chromodynamics（QCD）theory,the contributions of pions and gluons to the baryon mass are treated in second-order perturbation theory.In a nuclear many-body system,baryons interact with each other by exchangingσ,ω,andρmesons between quarks in different baryons.The strengths of u and d quark confinement poten-tials are determined by fitting the mass and radius of the free nucleon.As for s quark,its mass and strength of confinement potential are determined by fitting the masses ofΛ,Σ⁰,andΞ⁰in free space.In the work,four parameter sets about confinement potentials are obtained with four kind quark masses.We obtain the coupling constants between mesons and quarks by fitting the experimental data of the ground-state properties of40Ca,⁴⁸Ca,⁹⁰Zr,and²⁰⁸Pb and the coupling constants related to hyperons are deter-mined by single hyperon empirical potentials in nuclear matter at saturation density.In chapter 2,four parameter sets about the coupling constants between quarks and mesons are obtained with different quark masses,named QMF-NK0,QMF-NK1,QMF-NK2,and QMF-NK3.We study the properties of nuclei and nuclear matter with these parame-ter sets and it is found that three parameter sets of them can give satisfactory descriptions of ground-state properties of nuclei and saturation properties of nuclear matter,more-over the maximum masses of neutron stars without hyperon degree of freedom obtained are around 2.3M_⊙,and the corresponding radii are around 12.5 km.In chapter 3,we study the properties of singleΛand singleΞ⁰hypernuclei and strange nuclear matter with QMF-NK1S,QMF-NK2S,and QMF-NK3S sets,which are obtained by the single hyperon empirical potential at nuclear saturation density.Compared to the results from the QMF model without pion and gluon corrections,singleΛenergies inΛhypernuclei are more consistent with the experimental data.The properties ofΞ⁰hypernuclei are also calculated to serve as predictions for future experiments.The properties of neutron stars within strangeness degree of freedom are also investigated by these parameter sets through solving the Tolman-Oppenheimer-Volkoff equation.It is found that the maxi-mum masses of neutron stars with hyperons are around 2.1M_⊙,and the corresponding radii are around 13 km.