SHORT RANGE N-N INTERACTION IN THE CHIRAL BAG MODEL

Using the chiral bag model a quark theory of N-N interaction is formulated. In terms of the Green's functions of quark, gluon and Goldstone boson('pion')fields in the model,the effective nuclear potentials have been calculated for the different (TS) channels.There is a repulsive core in the potentials.The strength is about several hundreds MeV.About one fourth of the repulsion is due to 'pion' exchange.     

THE QCD BEHAVIOUR FOR THE VALENCE QUARK DISTRIBUTION FUNCTION OF PION IN THE LEADING LOGARITHM APPROXIMATION AND RELEVANT DIFFERENTIAL CROSS-SECTION

Using the analytic expression for valence quark distribution function of hadron in the leading logarithm approximation given by paper^[11], we discuss the QCD behaviour for the valence quark distribution function of pion. The existing data for valence quark distribution function of pion are explained excellently. We also predict the differential cross section M³ dσ/dM for massive lepton pairr production with Drell-Yan mechanism and compare it with data.     

CONTRIBUTIONS TO THE SHORT RANGE NUCLEAR FORCE FROPI THE QUARK-PION INTERACTION IN THE CHIRAL BAG MODEL

The contributions to the short range nuclear force from the quark-pion interaction in the Chiral Bag Model have been investigated.The antisymmetric wave functions for the physical channels of N-N, Δ-Δ and C-C are obtained in terms of the group classification and fractional parentage reduction. Assuming six quarks in a spherical bag, the separation of the quark triplets is described in terms of two orbitals-left and righ which are composed of the quark S and P states. The results show that the contribution to the short range nuclear force from one pion exchange of the quarks is repulsive about 150 MeV.     

LATTICE FORMULATION OF THE PURE GAUGE FIELDS ON COSET SPACE

In this paper we construct the lattice formulation of the pure gauge fields in a coset space in the cases of a group G with non-trivial topological property and of a chiral group G, and present a local gauge invariant action of a quark system on a fourdimensional Euclidean space lattice, which has the continuum limit as usual. For non-chiral group with trivial topological property, it is shown that the coset pure gauge fields have no influence on the confinement properties of the quark system by calculating latt-ice current-current propagztor when the coset pure gauge fields are retained manifest1y.     

SELF-ENERGY IN THE BAG MODEL

Based on the many-body theory of confined quarks and gluons^[l], the ultraviolet divergence of the self energy in the bag model is discussed. It is shown that for massless quark the self energy is finite and it is 1ogarithmically divergent for massive quark. The numerical calculation is performed for m=0 and m=1.0(in unit 1/R). The self energy has important effects on the bag model and changes the parameters in this model considerably. Furtherstudy of selfenergy and mass renormalization is necessary.     

K~ -核散射研究进展

本文简要回顾了K 核散射实验和理论方面近几年的研究进展。我们通过把介质中的K 核子相互作用与介质中的夸克凝聚联系起来 ,计算了K 核相互作用的非传统机制的贡献。结果表明核密度相关的介质内夸克凝聚可以解释K 核散射中的非传统介质效应。     

LATTICE FORMULATION OF THE PURE GAUGE FIELDS ON COSET SPACE

In this paper we construct a lattice formulation of the pure gauge fields on a coset space in the cases of a group G with non-trivial topological property and of a chiral group G, and present a local gauge invariant action of a quark system on a four-dimensional Euclidean space lattice, which has the continuum limit as usual. For non-chiral group with trivial topological property, it is shown that the coset pure gauge fields have no influence on the confinement properties of the confinement properties of the quark system by calculating lattice current-current propagator when the coset pure gauge fields remain manifest.     

THE DISCUSSION ON SOLVING THE COUPLING EQUATIONS WITH COLOR VAN DER WAALS FORCE IN THE QUARK POTENTIAL MODEL

The second order homogeneous ordinary differential equations were derived by indroducing the Gaussian type quark confinement potential in order to study color-analog Van der waals force in N-N interaction. In this paper, it is proved theoretically that the existence and uniqueness of non-zero solution of problem of boundary value in this kind of equations and the non-zero solution are calculated by numerical method (Gill method).     

THE CONVERSION OF GLUONS INTO QUARKS AND THE MULTIQUARK STATES

The rate for the conversion of the gluon into a color octet quark pair which subsequently forms a multiquark state with another quark pair or a gluon is discussed. The static potential in a [(QQ)₈(qq)_8,1] state where Q=c,b and q=u, d is studied in the MIT bag model. It is shown that the repulsive Coulomb force between Q and Q is dominant at small QQ separations, which would significantly suppress the QQ wave function at the origin. For the charm quark (Q=c) the ratio of |Ψ(O)|² for the ordinary (QQ)₁ to that for the(QQ)₈ in the [(QQ)₈(qq)_8,1] state is estinated to be 2-5. Therefore the assumption |Ψ₈(O)|²=|Ψ₁(O)|² would lead to an overestimation for the rate of g*→QQ and it is necessary to take the suppression effect of the repulsive Coulomb force into consideration.     

THE COLLIDING COMPONENT IN SOFT HADRONIC INTERACTIONS

The key role of the colliding component in soft hadronic interactions is studied. The different colliding components are found to display quite different distributions for both effective energy and fragmentation baryon momentum. After the calculation of the resonance decay correction to these distributions, a principle and method, which can directly decide the colliding component according experimental data are given. The data now available seem to rule out valence quark and support constituent quark as colliding component.     

THE ANALYSIS OF THE PHASE TRANSITION MECHANISM IN THE EARLY UNIVERSE

Ideal first-order phase transition and non-ideal phase transition that have supercooling quark phase in the early universe are analysed.The phase transition time in the two scenario are given.     

Gluon and quark jets in a recursive model motivated by quantum chromodynamics

We compute observable quantities like the multiplicity and momentum distributions of hadrons in gluon and quark jets in the framework of a recursive cascade model, which is strongly motivated by the fundamental interactions of QCD. Fragmentation occurs via 3 types of breakups: quark → meson+ quark, gluon→meson+gluon, gluon→quark+ antiquark. In our model gluon jets are softer than quark jets. The ratio of gluon jet to quark jet multiplicity is found to be 2 asymptotically, but much less at lower energies. Some phenomenological consequences for λ decay are discussed.     

Deconfinement phase transition in neutron star matter

The transition from hadron phase to strange quark phase in dense matter is investigated. Instead of using the conventional bag model in quark sect, we achieve the confinement by a density-dependent quark mass derived from in-medium chiral condensates, with a thermodynamic problem improved. In nuclear slot, we adopt the equation of state from Brueckner-Bethe-Goldstone approach with three-body force. It is found that the mixed phase can occur, for reasonable confinement parameter, near the normal saturation density, and transit to pure quark matter at 4-5 times the saturation, which is quite different from the previous results from other quark models that pure quark phase can not appear at neutron-star densities.     

Geometry of Quark and Strange Quark Matter in Higher Dimensional General Relativity

In this paper we study quark matter and strange quark matter in higher-dimensional spherical symmetric space-times. We analyze strange quark matter for the different equations of state and obtain the space-time geometry of quark and strange quark matter. We also discuss the features of the obtained solutions in the context of higher-dimensional general theory of relativity.     

THE WAVE EQUATIONS AND MASS SPECTRA OF BARYON STATES IN THE QUARK MODEL

The independent particle approximation is used to treat the bound state problems in the quark model. The solution for meson states obtained in this approximation is the same as that obtained from the Bethe-Salpeter equation. The solution for the baryon states is also obtained. The mass spectra of mesons and baryons determined from these equations are in agreement with the experiment.     

Properties of the top quark

The top quark was discovered at the CDF and D0 experiments in 1995. As the partner of the bottom quark its properties within the Standard Model are fully defined. Only the mass is a free parameter. The measurement of the top quark mass and the verification of the expected properties have been an important topic of experimental top quark physics since. In this review the recent results on top quark properties obtained by the Tevatron experiments CDF and D0 are summarised. At the advent of the LHC special emphasis is given to the basic measurement methods and the dominating systematic uncertainties.     

Wigner Distributions in Light-Front Quark Models

We discuss the quark Wigner distributions which represent the quantum-mechanical analogues of the classical phase-space distributions. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse momentum dependent parton distributions, which encode the most general one-body information of partons in momentum space. In particular, we present a study within light-front quark models. The quark orbital angular momentum is also obtained from the phase-space average of the orbital angular momentum operator weighted with the Wigner distribution of unpolarized quark in a longitudinally polarized nucleon. The corresponding results calculated within different light-front quark models are compared with alternative definitions of the quark orbital angular momentum as given in terms of generalized parton distributions and transverse momentum dependent parton distributions.     

Quark Loop Effects on Dressed Gluon Propagator in Framework of Global Color Symmetry Model

Based on the global color symmetry model (GCM), a method for obtaining the quark loop effects on the dressed gluon propagator in GCM is developed. In the chiral limit, it is found that the dressed gluon propagator containing the quark loop effects in the Nambu-Goldstone and Wigner phases are quite different. In solving the quark self-energy functions in the two different phases and subsequent study of bag constant one should use the above dressed gluon propagator as input. The above approach for obtaining the current quark mass effects on the dressed gluon propagator is quite general and can also be used to calculate the chemical potential dependence of the dressed gluon propagator.     

THE PROPERTIES OF NUCLEAR MATTER AT LOW TEMPERATURE IN A POSSIBLE QUARK MECHANISM

In this paper,the nucleon is described by the MIT bag model,and the internal quark motion in the nucleon is modified by the scalar and vector meson fields.The Fermi motion of nucleon in nuclear matter is considered.The changes for intrinsic properties of nucleon in nuclear matter at different temperature are calculated as a function of the density.The binding energy per nucleon for different temperature is given.