πN Elastic Scattering and Resonances in Quark Potential Model

The quark potential model is used to investigate the low-energy elastic scattering of πN system. The model potential consists of the t-channel and s-channel one-gluon exchange potentials and the harmonic oscillator confining potential. By means of the resonating group method, a nonlocal effective potential for the πN system is derived from the interquark potentials and used to calculate the πN elastic scattering phase shifts. By considering the effect of QCD renormalization, the suppression of the spin-orbital coupling and the contribution of the color octet of the clusters （qq） and （qqq）, the numerical results are in fairly good agreement with the experimental data. The same model and method are employed to investigate the possible πN resonances. For this purpose, the resonating group equation is transformed into a standard Schrodinger equation in which the nonlocal effective πN interaction potential is included. Solving the Schrodinger equation by the variational method, we are able to reproduce the masses of some currently concerned πN resonances.

A Model-Independent Discussion of Quark Number Density and Quark Condensate at Zero Temperature and Finite Quark Chemical Potential

Generally speaking, the quark propagator is dependent on the quark chemical potential in the dense quantum chromodynamics （QCD）. By means of the generating functional method, we prove that the quark propagator actually depends on p4 ＋ iμ from the first principle of QCD. The relation between quark number density and quark condensate is discussed by analyzing their singularities. It is concluded that the quark number density has some singularities at certain # when T = 0, and the variations of the quark number density as well as the quark condensate are located at the same point. In other words, at a certain # the quark number density turns to nonzero, while the quark condensate begins to decrease from its vacuum value.

Quark confinement, new cosmic expansion and general Yang-Mills symmetry

We discuss a unified model of quark confinement and new cosmic expansion with linear potentials based on a general（SU3）color×（U1）baryon symmetry. The phase functions in the usual gauge transformations are generalized to new ‘action integrals＇. The general Yang-Mills transformations have group properties and reduce to usual gauge transformations in special cases. Both quarks and ‘gauge bosons＇ are permanently confined by linear potentials. In this unified model of particle-cosmology, physics in the largest cosmos and that in the smallest quark system appear to both be dictated by the general Yang-Mills symmetry and characterized by a universal length. The basic force between two baryons is independent of distance. However, the cosmic repulsive force exerted on a baryonic supernova by a uniform sphere of galaxies is proportional to the distance from the center of the sphere. The new general YangMills field may give a field-theoretic explanation of the accelerated cosmic expansion. The prediction could be tested experimentally by measuring the frequency shifts of supernovae at different distances.

Bottomonium states versus recent experimental observations in the QCD-inspired potential model

In the QCD-inspired potential model where the quark-antiquark interaction consists of the usual one- gluon-exchange and the mixture of long-range scalar and vector linear confining potentials with the lowest order relativistic correction, we investigate the mass spectra and electromagnetic processes of a bottomonium system by using the Gaussian expansion method. It reveals that the vector component of the mixing confinement is anticonfining and takes around 18.51% of the confining potential. Combining the new experimental data released by Belle, BaBar and LHC, we systematically discuss the energy levels of the bottomouium states and make the predictions of the electromagnetic decays for further experiments.

D^0D^^0＊(D^0D^0＊) system in QCD-improved many body potential

For a system of current interest（composed of charm, anticharm and a pair of light quarks）, we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to the D^0D^0＊ molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to 3872 Me V by introducing another parameter I0 that changes the strength of the interaction in this one component of X（3872）. The revised value of this second parameter can guide future trends in modeling of the full exotic meson X（3872）. We also report the changes with I_0 in the S-wave spin averaged cross sections for D^0D^0＊-→ωJ/ψ and D^0D^0＊-→ρJ/ψ. These cross sections are important regarding the study of QGP（quark gluon plasma）.

J/ψ-J/ψ scattering cross sections of quadratic and Cornell potentials

We study the scattering of J/ψ - J/ψ mesons using quadratic and Cornell potentials in our tetraquark(cccc)system.The system’s wavefunction in the restricted gluonic basis,which is written by utilizing the adiabatic approximation and Hamiltonian,is used via a quark potential model.The resonating group technique is used to obtain the integral equations,which are solved to obtain the unknown inter-cluster dependence of the total wavefunction of our tetraquark system.T-Matrix elements are calculated from the solutions,and eventually,the scattering cross sections are obtained using the two potentials.We compare these cross sections and find that the magnitudes of scattering cross sections of quadratic potential are higher than the Cornell potential.

Dissociation cross sections ofψ(3770),ψ(4040),ψ(4160),andψ(4415)mesons with nucleons

We study the dissociation of ψ(3770), ψ(4040), ψ(4160), and ψ(4415) mesons in collision with nucleons, which takes place in high-energy proton-nucleus collisions. The quark interchange between a nucleon and a ■ meson leads to the dissociation of the ■ meson. We consider the reactions:■, and■, where R stands for ψ(3770), ψ(4040), ψ(4160), or ψ(4415). A reaction of a neutron and a ■ meson corresponds to a reaction of a proton and the ■ meson by replacing the up quark with the down quark and vice versa. Transition-amplitude formulas are derived from the S-matrix element.Unpolarized cross sections are calculated with the transition amplitudes for scattering in the prior form and in the post form. The cross sections relate to nodes in the radial wave functions of ψ(3770), ψ(4040), ψ(4160), and ψ(4415) mesons.

Study on the mechanism of open-f lavor strong decays

Open-flavor strong decays are studied based on the interaction of a potential quark model. The decay process is related to the s-channel contribution of the same scalar confinement and one-gluon-exchange （OGE） interaction in the quark model. After we adopt the prescription of massive gluons in a time-like region from the lattice calculation, the approximation of four-fermion interaction is applied. The numerical calculation is performed to the meson decays in u, d and s light flavor sectors. The analysis of the DIS ratios of b1 →ωπ and a1 → ρπ shows that the scalar interaction should be dominant in the open-flavor decays.

Cross sections for inelastic K+ϕscattering

In the first Born approximation,we study the reactions Kφ→πK,ρK,πK*,and ρK*with quark-antiquark annihilation and creation.Transition amplitudes are derived with the development in the spherical harmonics of the relative-motion wave functions of two initial mesons and two final mesons so that parity is conserved and the total angular momentum of the final mesons equals that of the initial mesons.Unpolarized cross sections are calculated from the transition amplitudes that also contain mesonic quark-antiquark relative-motion wave functions and transition potentials for quark-antiquark annihilation and creation.The notable temperature dependence of the cross sections is shown.The cross sections for Kφ→ρK,Kφ→K*,and Kφ→ρK*may be of the millibarn scale,whereas the cross section for Kφ→πK is small.