Symposium On The Internal Spin Structure Of The Nucleon

After about three decades of experimental and theoretical efforts, the structure of the nucleon (proton and neutron) is now fairly well understood based on quantum chromodynamics, but only if averaged over its spin. As the recent “proton spin crisis” revealed, we do not understand much about the nucleon structure when its spin is polarized to a specific orientation. We expect that our understanding on this challenging problem will soon be significantly improved by the RHIC-Spin and other experiments in the near future, as well as by the lattice- and perturbative-QCD theoretical calculations. The purpose of this symposium was to summarize the current understanding and discuss the future perspective of this problem with experimental and theoretical physicists from both high-energy and nuclear physics communities.The symposium covered the overview of the structure studies, updates on the experimental results from CERN, SLAC, DESY, FNAL, and KEK, future experiments at RHIC, and recent theoretical developments (18 presentations, 113 participants).

This volume contains the proceedings of the GDH 2002 symposium. It is a review of the most recent results on the nucleon spin structure and related sum rules using real and virtual photons. The latest theoretical developments and the new high precision data from different laboratories are presented and discussed. The book provides a comprehensive picture of the nucleon spin studies from the perturbative domain down to the resonance and low momentum transfer region.

Containing the proceedings of the GDH 2002 symposium, this is a review of results on the nucleon spin structure and related sum rules using real and virtual photons. Theoretical developments and high precision data from different laboratories are presented and discussed. The work offers a comprehensive picture of the nucleon spin studies from the perturbative domain down to the resonance and low momentum transfer region.

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 history of spin in general, and of the nucleon spin structure in particular, has been full of surprises. For the past 25 years deep inelastic lepton scattering has been studied to determine the carriers of the nucleon spin. However, it was realized only recently that a full understanding of the nucleon spin will also require detailed information on the helicity structure in the resonance region, i.e. in the realm of nonperturbative QCD.This volume gives a status report on the spin structure in the nucleon resonance region, focusing on: new experimental results from SLAC and HERMES; a first glance at the JLab experiments to map out the spin structure functions at low and intermediate four-momentum transfers; the pioneering experiment at MAMI (Mainz) to determine the Gerasimov-Drell-Hearn sum rule for real photons; and recent theoretical concepts and investigations to describe the spin structure in the frameworks of higher twist expansion, phenomenological models and chiral perturbation theory.