Workshop"Multi-quark Hadrons; four, five and more?" Proceedings

Preface

YITP workshop entitled ``Multi-quark Hadrons; four, five and more?'' was held at Yukawa Institute for Theoretical Physics, Kyoto university, Feb. 17(Tue) -- 19 (Thu), 2004. This workshop was financially supported by Center for Diversity and Universality in Physics, Kyoto University. This web page is the proceedings of the workshop. In last two years, LEPS and BaBar announced the discoveries of exotic hadrons which may be regarded as 5- and 4-quark states, named Theta⁺ and D_s0, respectively. After then, various groups including ITEP(Russia), J-Lab(USA) and ELSA(Germany) also reported the data supporting the existence of the pentaquark hadron, and the exotic charmed meson was also supported by BELLE(KEK, Japan). In addition, last October, the existence of other possible pentaquark states was reported, which seemed to belong to the same multiplet as Theta⁺. The common characteristic of these exotic hadrons is their unusually narrow widths in comparison with their masses. These discoveries may imply unexpected rich structure of the hadron physics and provide us with challenges for deeper understanding of the dynamics of QCD. The main purpose of this workshop is to survey the experimental situation and the theoretical approaches to the multi-quark hadrons examined so far. Furthermore the workshop was also organized so that one can obtain broader perspectives of the physics related to multi-quark hadrons that has been opened by the new discoveries of the exotic hadrons. Thus this workshop covers a wide range of topics as follows:

Theta⁺ and physics of possible pentaquark hadrons
D_s0 and physics of possible tetraquark hadrons
The diquark correlations v.s. chiral dynamics; related topics include
- scalar mesons lighter than 1GeV
- H-dibaryon
- Color-Flavor Locked color superconductivity
What is the nature of the Lambda(1405)?; is the Lambda(1405) a ``molecular state''or a three-quark bound-state?
Physics of ``deeply bound Kaonic nuclei''predicted by Akaishi and Yamazaki and experimentally confirmed by Iwasaki et al; are they nine-quark states than hadron bound states?
Lattice QCD for exotic hadrons
Related topics

In spite of the short time between the announcement and the workshop, the number of the participants counted more than one hundred, which was beyond the expectation of the organizers. This fact may be taken as a proof that the workshop was timely and the way of the organization of the program was adequate. Although it seems that experimental and theoretical investigations are still needed for firmer confirmation of the existence and on the nature of the newly discovered multi-quark hadrons, we would be more than happiest if the workshop in retrospect will be taken as a cornerstone which defined the perspectives of the physics of multi-quark hadrons.

September, 2004

Editors:
Teiji Kunihiro, Tetsuya Onogi, H. Abuki and Toru T. Takahashi