Katsuhiko Suzuki

Ph.D (Tokyo Metroplitan University), Nuclear Physics (Theory)

I study theoretical nuclear and particle physics. It is of great interest to investigate the structure of the hadrons based on QCD and its effective theories. I study the high energy hadron scattering such as deep inelastic letpon-hadron scattering and the Drell-Yan process in order to probe non-perturbative hadron structure in detail.

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Research Topics

1. I study the quark structure of hadrons in terms of the low energy effective theory of QCD, e.g. the Nambu and Jona-Lasinio (NJL) model. I am specially interested in quark-quark correlation inside hadrons and its contribution to hadron properties. I have found that the correlation of spin-0 diquark, i.e. correlated two quark state, is quite strong from the symmetry consideration. I have shown that the phenomenological diquark model explains the baryon mass spectrum as well as the long standing problem of the non-leptonic weak transition with \Delta I=1/2 rule due to the strong spin-0 diquark correlation.

2. I study color confinement based on the field theoretical method. The knowledge of the quark confinement is necessary for the description of both low energy hadron physics and the high energy process. I consider the dual Meissner mechanism, suggested by the Abelian projection of QCD, and the analytical formulation of the lattice QCD.

3. I work on the high energy hadron processes such as the deep inelastic scattering and the quark fragmentation into hadrons. It is of my great interest to clarify a possible connection between the successful low energy quark model and the high energy hadron phenomena. I have studied the meson structure function within the NJL model, and obtained good agreements with experiments, where the non-perturbative effects are clearly seen. Then, I used the same procedure to calculate the nucleon structure function in the phenomenological diquark-quark model, and found the quark correlation is essential to reproduce a ratio of neutron to proton structure functions, as in the case of the non-leptonic weak transitions.

4. I have studied medium and off-shell effects on the pion structure function, motivated by the absence of the nucler pion enhancement in nucleus deep inelastic scattering. Calculations based on the NJL model shows that the pion structure function is almost unchanged in nuclear medium. This is because the Goldstone boson nature of the pion state. Off-shell effects on the pion structure function are more subtle. I have shown that the off-shell effect reduces the pion structure function substantially, though it is quite model dependent.

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