Gu Yun-Ting

Spin effects and N̄N annihilation effects in elastic antiproton-nucleus scattering

The differential cross section, the polarisation and the spin-rotation parameter in elastic scattering of 180 MeV antiprotons by 12C and 16O are calculated by means of Glaubers multiple scattering theory and Pauli-correlated wavefunction. The effects of N(mean)N annihilation are studied by using a phenomenological N(mean)N annihilation potential within this framework. The results indicate that spin effects are negligible at small angles but that at large angles spin effects improve the elastic angular distribution, and that the N(mean)N annihilation part of the amplitudes contributes significantly to the observables.

Upsilon Photo-Production off Proton in QCD Inspired Model

Based on the generalized vector meson dominance model in QCD, we study photoproduction of vector meson γ off the proton by use of the QCD inspired model in which the contributions from quark-quark, gluon-gluon, and quark-gluon interference term to observable are taken into consideration. Calculations are performed for total cross section σtot, differential cross section dσ/dt, ratio of the real part to imaginary part of forward scattering amplitude ρ, and nuclear slop parameter function β. The mediators of interactions between projectiles (the quark and antiquark pair fluctuated from the real the photon) and the proton target (three-quark system) are the tensor Glueball and Odderon instead of using the usual Pomeron exchange. The theoretical predictions for σtot (s) are consistent with the experimental data within error bars of the data. The data for dσ/dt, ρ, and β are urgently needed.

Pomeron-Quark Coupling from Charge Conjugation Invariance

Based on the charge conjugation invariance and the vacuum property of the Pomeron, we point out that the commonly used vector vertex of the Pomeron coupling to quark is incorrect since it contradicts with the Pomeron property. We also claim that the soft Pomeron could be a tensor glueball ξ(2230) with quantum numbers IG JPC = 0+ 2++ and total decay width Γtot ≌ 100 MeV, which lies on the soft Pomeron trajectory αp = 1.08 + 0.20t. Therefore, the coupling vertex of the soft Pomeron to quark should be tensorial which is invariant under the charge conjugation and can explain why the inadequate vector coupling, γμ, of the soft Pomeron to quark is successful in dealing with Pomeron physics.

Quark Mass Dependence of Nucleon Magnetic Moment and Charge Radii

Understanding hadron structure within the framework of QCD is an extremely challenging problem. Our purpose here is to explain the model-independent consequences of the approximated chiral symmetry of QCD for two famous results concerning the quark structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neutron are coincidental. That is, a relatively small change of the current quark mass would spoil both results.

Non-perturbative Aspects of QCD and Parameterized Quark Propagator

Based on the Global Color Symmetry Model, the non-perturbative QCD vacuum is investigated in the parameterized fully dressed quark propagator. Our theoretical predictions for various quantities characterized the QCD vacuum are in agreement with those predicted by many other phenomenological QCD inspired models. The successful predictions clearly indicate the extensive validity of our parameterized quark propagator used here. A detailed discussion on the arbitrariness in determining the integration cut-off parameter of µ in calculating QCD vacuum condensates and a good method, which avoided the dependence of calculating results on the cut-off parameter is also strongly recommended to readers.

Gasser–Leutwyler Coefficients of Chiral Lagrangian for Pseudoscalar Goldstone Bosons in Dyson–Schwinger Equations

Based on the Dyson–Schwinger equations of quark propagator in rainbow truncation with an effective gluon propagator, the ten unknown Gasser–Leutwyler coefficients of the chiral Lagrangian for pseudoscalar Goldstone bosons are predicted. The predicted values of Li with i = 1, 2, ..., 10 are in a reasonable agreement with empirical values used widely in literature, and the values predicted by many other theoretical models with QCD characteristics.

J/ψ and φ Electro-production in Pomeron Exchange Model

Based on Pomeron exchange model, J/ψ and φ production in electro-proton interaction are investigated with both linear and non-linear Pomeron trajectory. The experimental differential cross sections measured as a function of the kinematic variable Q2,W and t are reproduced successfully in the model. Our conclusions are that the Pomeron exchange model is a successful description of J/ψ and φ electro-productions on the proton, and that the linear trajectory is a good approximation to non-linearity of the Pomeron trajectory.

Antiproton-Nucleus Interaction and Coulomb Effect at High Energies

The Coulomb effect in high energy antiproton-nucleus elastic and inelastic scattering from 12C and 16O is studied in the framework of Glauber multiple scattering theory for five kinetic energies ranged from 0.23 to 1.83 GeV. A microscopic shell-model nuclear wave functions, Woods–Saxon single-particle wave functions, and experimental N amplitudes are used in the calculations. The results show that the Coulomb effect is of paramount importance for filling up the dips of differential cross sections. We claim that the present result for inelastic scattering of antiproton-12C is sufficiently reliable to be a guide for measurements in the very near future. We also believe that antiproton nucleus elastic and inelastic scattering may produce new information on both the nuclear structure and the antinucleon-nucleon interaction, in particular the -neutron interaction.

Vector Meson electro-production in Pomeron exchange model

Based on Pomeron exchange model, elastic production of vector meson in electro-proton interaction is investigated with both linear and non-linear Pomeron trajectory. A numerical calculation for J/psi production is performed. The effect of the energy scale so and photon virtuality Q(2) on differential cross section are also predicted. A good agreement with experimental data is obtained. Our conclusions are that the Pomeron exchange model is a successful description of J/psi electro-production, the dependence of the differential cross sections on Q2 is negligible, the linear trajectory is a good approximation to non-linearity of the Pomeron trajectory, and the value of the energy scale parameter so is dependent on the momentum transfer, namely its effect is moderate at low momentum transfer but it causes no difference at high momentum transfer vertical bar t vertical bar >= 1.25 GeV2.

Hyperspherical Analysis of D- in a Quantum Well

By introducing hyperspherical coordinates and assuming the quasiseparability of the hyperradius R from the angular variables Ω in the wavefunctions, we have solved the Schrodinger equation for a D- center in two dimensions to obtain the low-lying spectrum. The correlation patterns in these states are visualized.