Microscopic reaction dynamics for the study of heavy baryon structure

概要

In recent years the interests of hadron physics are concentrated on new heavy hadrons. Properties of many of the new heavy hadrons which contain charm and bot- tom quarks are still not known well, including exotic states that cannot be explained by a naive quark model for hadrons with two or three valance quarks. Therefore, in order to better understand the properties of these hadrons, theoretical and experimental researches on hadron spectroscopy are necessary. In these circumstances, hadrons which include both heavy and light quarks, provide a very good environment for theoretical research on hadron spectroscopy.

In the present thesis, a new microscopic mechanism for heavy baryon production reaction π− + p → M + Y is proposed where M is a pseudoscalar or a vector meson and Y is a strange or charmed baryon. We examine how the baryon structure plays a role in the productions of heavy baryons. For the charm production, E50 experiment at J-PARC is planned to measure the production of charmed baryons with a vector meson. Since it is possible to compare with existing experimental data on strange productions and the corresponding production reactions can occur in the J-PARC experiments, it is also worth to study the strange sector sufficiently.

The main content of the present thesis is to develop a two-quark microscopic process which is called two-quark process. The two quarks process is a reaction in which two quarks inside the baryon are directly involved in the production, in addition to the one-quark process which was studied previously. However, the production of the ρ modes has not been studied so far because, in the one-quark process, the only possible excitation is the λ mode. On the other hand, it is very important that the two-quark process can excite both λ and ρ modes. In the present thesis, first the research on heavy baryons and the one-quark process in the past is introduced and then based on this, we investigate the two-quark process for the reactions of the heavy baryon productions. We calculate the production rates of various heavy baryons and discuss the relation between the structure and the production rates. We also discuss general features of the one-quark process and the two-quark process.