BARYONS S y s t e m a t i z a t i o n a n d M e t h o d s o f A n a l y s i sMesons and Baryons Downloaded from www.worldscientific.com by 18.236.120.13 on 05/10/18. For personal use only. British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. PrefaceThe notion of quarks appeared in the early sixties just as a tool for the systematisation of the growing number of experimentally observed particles. First it was understood as a mathematical formulation of the SU(3) properties of hadrons, but soon it became clear that hadrons have to be considered as bound states of quarks (objects which we call now "constituent quarks"). The next steps in understanding the quark-gluon structure of hadrons were made in the framework of Quantum Chromodynamics, a theory of coloured particles, as well as in the study of hard processes (i.e. in the study of hadron structure at small distances). We know that hadrons are, definitely, composed of large numbers of quarks, antiquarks and gluons. We have learned this from deep inelastic scattering experiments, and this picture is proven by many experiments on hard collisions and multiparticle production. At small distances quarks and gluons interact weakly, obeying the laws of QCD. An important fact is that a coloured quark or a gluon alone cannot leave the small region of the size of a hadron (i.e. that of the order of 10 −23 cm): they are confined -they can fly away only in groups which are colourless.In the fifties and sixties of the last century virtually the whole physics of "elementary particles" (at that time also hadrons were considered as such) was devoted to the consideration of these distances. With the progress of experimental physics very soon even smaller distances were reached at which hard processes were investigated, giving a strong basis to Quantum Chromodynamics -a theory in the framework of which coloured particles can be considered perturbatively. This, and the hope that the key for understanding the physics of strongly interacting quarks and gluons was hidden just here, initiated research towards smaller and smaller distances, skipping the region of strong (soft) interactions. We accumulated a very serious amount of knowledge on the hadron structure at extremely small distances. But looking back to the region of standard hadron sizes, 10 −24 -10 −23 cm, we realize now that, in fact, the physics at ∼ 10 −23 cm in its essential domains remains unknown [1, 2]. We left behind the hadron distances without really understanding all the observed phenomena. We have learned only a small part of what could be learned from the experimental results in that region, not to mention that experiments which could be easily carried out were also abandoned. The physics community just skipped some p...

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Some auxiliary material has been relegated to the Appendices and could probably aid the reader in making various explicit calculations. We would like to thank A.A. Anselm, I.M. Dremin, S.S. Gerstein, V.G. Grishin, E.M. Levin, N.N. Nikoiaev, M.G. Ryskin, E.V. Shuryak for extremely helpful discussions of the problems considered in the book. We are also deeply indebted to V.N. Gribov: his comments were extremely helpful for us. We are happy to thank our friends and colleagues V.M. Braun, L.G. Dakhno, A.K. Likhoded and P.E. Volkovitski: some papers written in collaboration with them are reflected in this work. The authors are grateful to K.K. Phua for his encouragement in writing this book. Two of us (V.V.A. and Yu.M.S.) are much obliged to 0.1. Sumbaev for the permanent support of the investigations presented here: the book could hardly be accomplished without it. We are specially indebted to our deceased friend V.M. Shekhter. Our collaboration with him has provided much material which is being passed on in this book. This book is dedicated to his memory.

Non-strange and strange pentaquaks with hidden charm are considered as diquarkdiquark-antiquark composite systems. Spin and isospin content of such exotic states is discussed and masses are evaluated.