Nucleon—Nucleon Phase Shifts in the Extended Quark—Delocalization Colour—Screening Model

An alternative method is applied to the study of nocleon-nucleon scattering phase shifts within the framework of the extended quark delocalization colour-screening model,in which the one-pion exchange with short-range cutoff is included.     

Colour Conductivity of a Quark Plasma at Finite Chemical Potential

We apply non-Abelian transport theory to a low-temperature case,and discuss the colour electric dynamics of cold-dense quark matter at large chemical potential.Finally,at leading logarithmic accuracy,the colour conductivity dependence on chemical potential is obtained.     

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

Based on the global color symmetry mode/ （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 shouM 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.     

Chemical Potential Dependence of the Dressed—Quark Propagator from an Effective Quark—Quark Interaction

We exhibit a method for obtaining the low chemical potential dependence of the dressed quark propagator from the dressed-quark propagator,which provides a means of determining the behavior of the chiral and deconfinement order parameters.A comparison with the results of previous researches is given.     

Diquark Structure of Pentaquark in the Quark Delocalization Colour Screening Model

In the framework of quark-delocalization, colour-screening model, the diquark structure of pentaquark θ^＋ is studied in detail under the adiabatic approximation. The calculation is carried out by using the fractional parentage expansion technique, which greatly simplify the calculation of the matrix elements of Hamiltonian. The results show that the ground state of the pentaquark has negative parity rather than positive parity, which was proposed by daffe-Wilczek. However the mass obtained is about 1651 MeV which is still higher than the observed mass 1540 MeV.     

Formation Region and Amplitude of Colour Superconductivity in an Instanton—Induced Model

Colour superconductivity is investigated in the frame of a two flavour instanton-induced model.The ratio of diquark to quark-antiquark coupling constants is restricted to be c/(Nc-1) with 1≤c≤2.87 and controls the formation region and amplitude of colour superconductivity.While the finite current quark mass changer the chiral transition significantly,it does not considerably change the colour superconductivity.     

Gluon Transport Properties in the Region of Coexistence of Both Hadronic and QGP Phases

The transport properties of gluon in color space in a system of coexistence of both hadronic and QGP phases are investigated from the quantum transport equation of gluon.     

Does There Exist Only One Solution of the Dyson-Schwinger Equation for the Quark Propagator in the Case of Non-Zero Current Quark Mass

It is shown on general ground that there exist two qualitatively distinct solutions of the Dyson-Schwinger equation for the quark propagator in the case of non-zero current quark mass. One solution corresponds to the “Nambu- Goldstone” phase and the other one corresponds to the “Wigner” phase in the chiral limit.     

Dilepton Production in a Chemically Equilibrating Quark—Gluon Matter

We have studied dilepton production in a chemically equilibrating quark-gluon matter produced at RHIC energies.We find that the dilepton yield is no longer a monotonically decreasing function of the initial quark chemical potential.Therefore,the dilepton suppression may not be useful as a signature for quark-gluon matter formation.     

Colour Dipole Picture for Deep Inelastic Scattering in the Collinear Factorization Scheme

The colour dipole picture for deep inelastic scattering processes is generalized in the collinear factorization scheme.We show that a duality between the colour dipole picture and scattering picture is lost in higher twist amplitudes.     

A Monte Carlo Study on the Identification of Quark and Gluon Jets

Three-jet events in e^ e^- collisions at 91.2 GeV are investigated using both HERWIG and JETSET Monte Carlo generators.The angles among the three jets are used to identify the quark and gluon jets.An analysis at the parton level is carried out to ensure the reasonableness of this method and an angular cut is utilized to improve the purity of this identification.The multiplicity inside the identified quark or gluon jets agrees with the quantum chromodynamic predictions qualitatively.     

Top Quark Pair Production at e^＋e^— Colliders in the Topcolor—Assisted Technicolor Model

In the framework of topcolor-assisted technicolor model we calculate the contributions from the preudo Goldstone bosons and new gauge bosons to e^ e^-→ttk.We find that for reasonable ranges of the parameters,the preudo Goldstone bosons afford dominate contribution,the correction arising from new gauge bosons is negligibly small,the maximum of the relative corrections is-10% with the center-of-mass energy √s=500GeV;whereas in the case of √s=1500 GeV,the relative corrections could be up to 16%.Thus large new physics might be observable at the experiments of next-generation linear colliders.     

Thermal Charmed Quark Contribution to Dileptons in Chemically Equilibrating Quark—Gluon Matter

We find that in a chemically equilibrating baryon-rich quark-gluon matter, due to the slow cooling rate, high initial temperature, large gluon density as well as large fusion cross section of gg→cc^- in the intermediate mass region, the gluon fusion gg→cc^- provides a dominant contribution to dileptons with intermediate masses, resulting in the significant enhancement of intermediate mass dileptons.     

Tachyon Pole in σ Meson Propagator in Nuclear Matter in the Relativistic σ—ω Model

The conditions that the tachyon pole of the σ meson propagator in nuclear matter appears are studied in the one-loop approximation in the relativistic σ-ω model.Different from the results of the previous paper,we find that the effect of the constant a in the self-interaction,U(σ)=aσ 1/2! bσ^2 1/3!cσ^3 1/4!dσ^4,of the σ meson cannot be neglected.It determines the critical density where techyon appears.The smaller the a,the larger the critical density.The binding energy,pressure,incompressibility coefficient,nucleon effective mass are calculated and the relation between parameters to the tachyon pole is also studied.     

Chemical Potential Dependence of the Dressed-Quark Propagator in a Simple Confining QCD Model

Based on the Dyson-Schwinger approach, a method for obtaining the chemical potential dependence of the dressed quark propagator in the ‘Nambu-Goldstone‘ and the ‘Wigner‘ phase is developed. The bag constant in the presence of the non-zero chemical potential is analysed.     

Electron—Phonon Coupling in Anion Metallic Solids and Superconducting MgB2

We analyse the Hopfield factor of the newly found superconductor MgB2 using the linear muffin-tin orbital method.Based on a uniform transferred charge density model raised,it is shown from our calculation that the high difference of electronegativity between boron and magnesium favours the high l(l 1) angular momentum hybridization and then the Hopfield factor.Our analysis is consistent with experimental results.Comparisons with cuprate superconductors are also discussed.     

J／φ→γBB Decays and the Quark—pair Creation Model

We generalize the quark-pair creation model to a study of the radiative decays J/φ→γBB by assuming that the u.d,or s quark pairs are created with the same interaction strength,From the calculation of the ratio of the decay widths （J/φ→γpp)/Γ（J/φ→pp),we extract the quark-pari creation strength gI=15.40GeV,Based on the SU(6)spin-flavour basis and the “uds” basis,the radiative decay branching ratios cotaining strange baryons are evaluated.Measurements for these decay widths from the BESII data are suggested.     

Topological String in Quantum-Chromodynamical Chiral Phase Transitions

It is pointed out that if in heavy ion collision processes, the quark-gluon plasma SU(2) chiral phase transition really takes place and the phase transition is a second order. Then the topological string, i.e., the π string, will be formed. The main effect of this phenomenon is that there will be a number of pions produced by decay of the π string in the final state. The pions from the decay of the π string lead to the same effect of decreasing the Hanbury-Brown-Twiss peak in two-pion spectra which is just as that of the long-lived hadronic resonances.At relativistic heavy-ion collision and large hadron collision energies, it is expected that the factors are about α ∽ 0.7 - 0.9 and α ∽ 0.6 - 0.85, respectively.