Preface
The CLXVII Course “Strangeness and Spin in Fundamental Physics” of the “Enrico Fermi” School, held in Varenna from June 19 to 29, 2007, was dedicated to the discussion of the role played by two subtle and somehow puzzling quantum numbers, the Strangeness and the Spin, in Fundamental Physics. They both relate to basic properties of the fundamental quantum field theories describing strong and electro-weak interactions and to their phenomenological applications. In some instances, like the partonic spin structure of the proton, they are deeply correlated.
The concept of Strangeness was introduced in 1953 in order to explain experimental observations in Particle Physics, which could not be interpreted without the introduction of such a new quantum number. Strangeness was the paradigm for the introduction, in the following decades, of other new quantum numbers (Charm, Beauty, …) and may be considered as the cornerstone for the building up of the presently accepted theory of strong interactions, QCD, and of the quark content of matter.
However, it was soon realized that Strangeness plays a crucial role not only in elementary systems, but also in much more complicated many-body ensembles (nuclei, atoms, neutron stars, …). Due to the circumstance that the mass of the s-quark is somewhat between the masses of the light u- and d-quarks (from which our world is built) and those of the heavy c−, b− and t-quarks, exotic many-body systems containing s-quarks may be assembled and carefully examined experimentally. The study of their properties is of fundamental importance for understanding their underlying structure. The physics of Strangeness then encompasses the fields of Elementary Particles, Nuclear Physics, Atomic Physics and Astrophysics, with close and important links between them.
The concrete demonstration of the great importance gained by the Strangeness Physics is given by the great number of large experiments partially or fully devoted to it at large Laboratories like RHIC-BNL, TJNAF, DAPHNE, GSI, Nuclotron-Dubna. Even more, the powerful complex of accelerators J-PARC, under completion at Tokai (Japan) which will supply in two years beams of mesons, in particular Kaons, of unprecedented intensity and purity, will dedicate a large amount of time to Strangeness Physics studies.
Half of the lectures and seminars of the Course covered many aspects of the Strangeness Physics, and were given by world-recognized experts in the field: Professors Bendiscioli, Bertini, Bressani, Feliciello, Gal, Guaraldo, Nagae, Nappi and Schramm.
The interest in Spin Physics has enormously grown in the last 15-20 years, both from the experimental and theoretical points of view. In all high-energy experimental facilities there are ongoing or planned spin-dedicated experiments with collisions of polarized particles: HERMES at DESY, STAR and PHENIX at RICH-BNL, several experiments at TJNAF. Even BELLE, at KEK, studies spin effects in the fragmentation of quarks produced in e+e− interactions. Collisions between polarized protons and polarized antiprotons have been proposed for future experiments at GSI: these would explore entirely new aspects of the strong interactions and QCD. Experiments with polarized protons are also planned at J-PARC.
The many puzzling results recently obtained by measuring several spin asymmetries have stimulated enormous progress in the study of the spin structure of protons and neutrons. Intense theoretical activity has discovered new features of non-perturbative QCD, like strong correlations between the spin and the intrinsic motions of quarks inside the nucleons. The high-energy spin physics community is aiming at reaching a full understanding of the proton structure, which not only takes into account the longitudinal degrees of freedom, but also transverse motions, spin and orbital angular momenta of quarks and gluons.
The other half of the lectures and seminars of the Course was devoted to many facets of high-energy spin physics, and were given by excellent speakers and active researchers in the field: Professors Anselmino, Avagyan, Boglione, Hash, Jaffe, Leader, Saito and Vogelsang.
The purpose of the Course was that of providing a complete, updated and critical account of the most recent and relevant discoveries in the above fields, both from the experimental and theoretical sides, and was fully achieved. The Course was very timely and important for the Enrico Fermi School, focused on education and information and providing a careful analysis of the available data, predictions for ongoing experiments and suggestions for future plans.
In conclusion the organizers of the Course warmly thank the European Project Hadron Physics of the FP6 framework and the Project HYPERGAMMA of PRIN (Italian Ministry of Research) for the generous financial support to the School, which made its organization possible. Special thanks are due to Miss B. Alzani for the continuous and invaluable help during the Course, as well as to Miss G. Bianchi Bazzi, Miss R. Brigatti, Mr. D. Caffarri of the Villa Monastero organization. Mrs. M. Missiroli and Mrs. C. Vasini are also acknowledged for their precious activity before and after the completion of the Course. Finally special acknowledgements are due to Dr. A. Feliciello and Prof.Ph.G. Ratcliffe, Scientific Secretaries of the Course, for their continuous, patient and precious work at all stages of the scientific and practical organization.
M. Anselmino and T. Bressani