Search

The recent measurement of quark-hadron duality is shortly discussed by using a simple constituent quark model. Comparing with the moments of the structure functions in the resonance region and in the deep inelastic scattering region, we study the occurances of Bloom-Gilman quark-hadron duality for the nucleon structure function F2 and g1. Local duality is also analyzed.

To extract the polarized gluon distribution Δg, we study the large–pTlight hadron pair productions in polarized semi-inclusive reaction, which are dominantly produced via 2 mechanisms: photon–gluon fusion(PGF) and QCD Compton. The PGF gives us a direct information on Δg in the nucleon, whereas QCD Compton is background to the signal process for extracting Δg. By using symmetry relation among fragmentation functions and taking an appropriate combination of light hadron pair production processes, we can remove an effect of QCD Compton from those cross sections. Here we propose a new formula for extracting Δg from those processes.

Recent studies on the newly observed resonance [Formula: see text] with a compact structure in a chiral SU(3) constituent quark model are briefly reported. the overall properties, including the mass, the partial decay widths in various decay modes, and the total width, comparing with the experimental data, show that a compact hexaquark dominated structure might be a reasonable interpretation for this state. Moreover, the charge distribution of [Formula: see text] is also discussed.

Spin-dependent relativistic effect on binding and dissociation properties of heavy quarkonium in a thermal environment is investigated. The result shows that fine and hyperfine interactions influence the description of the thermal properties of the heavy quarkonium, such as ηc and J/ψ.

The contribution due to the Debye screening to the dissolution of heavy-quark resonances is studied by using the two different binding potentials at finite temperature in a nonrelativistic approximation. The critical values of the Debye screening length are calculated. Our calculations show that the critical values of the Debye screening length depend on the forms of the quark binding potential at finite temperature. We also estimate the critical temperature for deconfinement of heavy-quark resonances. The effects of different quark binding potentials on the dissolution for heavy-quark resonances are discussed and compared to the previous results.

By utilizing the screened potential model, the spectra and decay properties of hydrogen-like mesons [Formula: see text] are studied. The calculated ratio of M1 decay widths for the D*+ and D*0 mesons is 0.0286. This result is much smaller than the data of MARK3 in 1988, but agrees with the observed data of CLEO in 1992. The result indicates that the contradiction between the calculated result and the data of MARK3 for hydrogen-like mesons in the quark model can be understood, if future experiment can confirm the data of CLEO in 1992.