Semirelativistic Constituent Quark Model With Goldstone Boson Exchange Hyperfine Interactions

The Workshop N* Physics and non-perturbative QeD was held at the Eu ropean Center for Theoretical Studies and Related Areas (ECT*) in Trento, Italy, during May 18-29, 1998. Previous workshops of the series on N* Physics took place at the Florida State University (1994), at CEBAF (1995), at the Institute for Nuclear Theory in Seattle (1996) and at the George Washington University (1997). The Workshop was devoted to a summary of recent experimental and the oretical research on N* phsyics and special emphasis was given to the infor mation that photo-and electro-production of nucleon resonances can provide on the non-perturbative regime of Quantum Chromodynamics. The idea was to stimulate discussions among experimentalists and theoreticians in order to pursue the interpretation of the huge amount of forthcoming data from several laboratories in the world. It was therefore decided to have both experimental and theoretical lectures on the main topics, like ,among the others, single and double pion production, TJ-and K-meson production, the GDH sum rule, the spin of the proton, etc. Thanks to the unusual two-week extension of the Work shop, the allotted time for the lectures was extended up to one hour in order to allow the invited lecturers to give a detailed presentation of their topics. Fi nally, various short contributions were selected to sharpen the discussion about selected items.

Abstract: The set of parameters used in the Goldstone-boson-exchange (GBE) model of quark-quark interactions by a group from the University of Graz to calculate baryon energy spectra is not optimal. A systematic approach to optimize these free parameters for a greater collection of baryons than previously treated is presented here. The baryons considered possess a physical symmetry where their constituent quarks are either made of all identical quarks or just two identical quarks. In order to calculate the various energy states of these baryons, the Faddeev method is used under the premise that three-quark interactions are modeled by an infinitely rising confinement potential. The new parameters and resulting energy calculations obtained yield better agreement with experimental data than previously achieved. In addition to providing a stronger case for the GBE model, these newfound parameters have the potential to give further insight into how quarks interact and pave the way for more advanced work in the field of three-quark problems.

This volume encompasses current issues in the physics of baryons, including their spectroscopy and quark-gluon substructure, and investigations with electroweak and strong interacting probes. The topics covered are: Baryon and Meson Spectroscopy, Chiral Physics, Heavy Quarks, Deep Inelastic Scattering, Form Factors and Exclusive Processes, Hadron-Nucleon Interaction, Hadrons in Nuclear Medium, and Special Topics in the First and Second Resonance, as well as a special part on the current status of neutrino physics. Each topic begins with an Introduction and Overview so as to make the more specialized papers readily accessible to non-experts.

The structure of light hadrons is dominated by the spontaneously broken chiral symmetry of the strongly interacting (QCD) vacuum. Low energy properties of light hadrons can be described in terms of quarks interacting with chiral fields. This book gives a comprehensive account of a large class of models which describe the restoration of chiral symmetry at high temperature and density, the effective interactions between quarks, mesons as solutions of the Beth-Salpeter equation, and baryons in terms of solitions which rotate in flavor space. An in-depth analysis of regularization is given, including regularization by delocalized fields. Symmetry conserving approximations are formulated using both path integral and Feynmann graph methods. The book's style is pedagogical and well-suited to graduate and Ph.D. students who want to learn the techniques used in present day research. It can also serve as a reference for research and lecture courses.

From 5 to 15 August 1984, a group of 79 physicists from 61 laboratories in 26 countries met in Erice for the 22nd Course of the International School of Subnuclear Physics. The countries represented were Austria, Belgium, Brazil, Bulgaria, Canada, People's Republic of China, Denmark, the Federal Republic of Germany, France, Greece, Hungary, Iran, Israel, Italy, Japan, Korea, Malaysia, Mexico, the Netherlands, Pakistan, Poland, Sweden, Switzerland, Turkey, the United Kingdom, the United States of America. The School was sponsored by the Italian Ministry of Public Education (MPI), the Italian Ministry of Scientific and Technologi cal Research (MRST), the Regional Sicilian Government (ERS), and the Weizmann Institute of Science. The programme of the School was devoted to a review of the most significant results in theoretical and experimental research work on the interactions between what we believe today are the point like constituents of the world: quarks and leptons. It should however not be forgotten that many problems are still to be understood: especially in the forefront of the correla tion between quarks and leptons. This game started in 1966 with the proposal for "leptonic quarks" and went on with "preons" and "rishons" just to quote the most famous attempts to unify these two worlds.

The conference NSTAR 2000 was part of a series of conferences and workshops that began in New York in 1988. Since then, the field of excited nucleons and hadron structure has developed enormously, and the scope has broadened. Most significantly, new experimental facilities have come into operation, allowing precise measurements of resonance couplings and transition form factors. The search for ?missing? quark model states and gluonic excitations in complex hadronic channels is now possible.On the theory side, new and promising developments have emerged: quark models with meson degrees of freedom, hybrid baryon models, and studies of baryons in the limit of many colors. For the first time, lattice QCD has been employed to calculate masses of excited nucleons. Nucleon resonances are now recognized as providing significant contributions to the nucleon spin sum rules, as well as the Gerasimov-Drell-Hearn and Bjorken integrals, at finite momentum transfer.

The sixteenth European Conference on Few Body Problems in Physics has taken place from June 1 to June 6, 1998, in Autrans, a little village in the mountains, close to Grenoble. The Conference follows those organized in Peniscola (1995), Amsterdam (1993), Elba (1991), Uzhgorod (1990) ... The present one has been organized by a group of physicists working in different fields at the University Joseph Fourier of Grenoble who find in this occasion a good opportunity to join their efforts. The core of the organizing committee was nevertheless located at the Institut des Sciences Nucleaires, whose physicists, especially in the group of theoretical physics, have a long tradition in the domain. The Few Body Conference has a natural tendency to be a theoretical one - the exchange about the methods used in different fields is the common point to most participants. It also has a tendency to be a hadronic physics one - the corresponding physics community, perhaps due to the existence of experimen tal facilities devoted to the study of few body systems, is better organized. In preparing the scientific program, we largely relied on the advices of the Inter national Advisory Committee, while avoiding to follow these trends too closely.

This is an updated version of the book published in 1985. QCD-motivated, it gives a detailed description of hadron structure and soft interactions in the additive quark model, where hadrons are regarded as composite systems of dressed quarks. In the past decade it has become clear that nonperturbative QCD, responsible for soft hadronic processes, may differ rather drastically from perturbative QCD. The understanding of nonperturbative QCD requires a detailed investigation of the experiments and the theoretical approaches. Bearing this in mind, the book has been rewritten paying special attention to the interplay of soft hadronic collisions and the quark model. It is at the crossroads of these domains that peculiar features of strong QCD reveal themselves. The book discusses constituent quarks, diquarks, the massive effective gluons and the problem of scalar isoscalar mesons. The quark-gluonium classification of meson states is also given. Experimentally observed properties of hadrons are presented together with the corresponding theoretical interpretation in the framework of the composite hadron structure. The text includes a large theoretical part, which shows how to treat composite systems (including relativistic ones) with a technique based on spectral integration. This technique provides the possibility of handling hadrons as weakly bound systems of quarks and, at the same time, takes into account confinement. Attention is focused on the composite structure revealing itself in high energy hadron collisions. Fields of applicability of the additive quark model are discussed, as is colour screening in hadronic collisions at high and superhigh energies. Along with a detailed presentation of hadronOCohadron collisions, a description of hadronOConucleus collisions is given. Sample Chapter(s). Chapter 1: Introduction (1,047 KB). Contents: High Energy Hadron Interactions; Composite Systems; High Energy Interactions of Composite Systems; Hadron Zoology and Static Features of Hadrons; Binary Processes in the Quark Model; Multiparticle Production in the Quark Model: Hadron Collisions at Moderately High Energies; HadronOCoNucleus Collisions. Readership: Graduate students and researchers in particle and nuclear physics."

Clues in the search for a fundamental description of hadron physics based on QCD may be obtained from a phenomenological constituent quark model in which the color-electric force binds quarks into saturated color-singlet hadrons, and finer details of the spectrum and multiquark physics are dominated by the color-magnetic hyperfine interaction. 47 refs.