Nucleon Structure At Large Bjorken X

Marseille, France, 26-28 July 2004

The main purpose of the conference was to improve our understanding of the nucleon structure in the valence quark region, namely where the Bjorken x variable is large, a region so far poorly known. Many theoretical ideas were presented and suggestions were made for new experiments in present facilities or in future high luminosity machines. Recent data from several laboratories were shown for the first time and discussed extensively, which witnessed substantial progress in this field.

These proceedings will be of interest to researchers in nuclear and high-energy physics and graduate students. This workshop focused on the latest developments in the study of the quark structure of the nucleon at large Bjorken x, usually called the valence region. Its main purpose was to bring together experts for an in-depth and critical review of recent advancements in this field of research. This was particularly important in view of the upcoming energy upgrade of Jefferson Lab whose research program will continue to further our understanding of the inner structure of the nucleon.

As the only stable baryon, the nucleon is of crucial importance in particle physics. Since the nucleon is a building block for all atomic nuclei, there is a need to analyse the its structure in order to fully understand the essential properties of all atomic nuclei. After more than forty years of research on the nucleon, both the experimental and theoretical situations have matured to a point where a synthesis of the results becomes indispensable. Here, A.W. Thomas and W. Weise present a unique report on the extensive empirical studies, theoretical foundations and the different models of the nucleon. The appendices provide an extensive summary of formulae needed in practical calculations. From the contents: electromagnetic structure of the nucleon, weak probes of nucleon structure, deep inelastic lepton scattering on the nucleon; elements of QCD, aspects of non-perturbative QCD, Chiral Symmetry and nucleon structure, models of the nucleon

This graduate/research level book describes our present knowledge of protons and neutrons, the particles which make up the nucleus of the atom. Experiments using high energy electrons, muons and neutrinos reveal the proton as being made up of point-like constituents, quarks. The strong forces which bind the quarks together are described in terms of the modern theory of quantum chromodynamics (QCD), the â€~glue' binding the quarks being mediated by new constituents called gluons. Larger and new particle accelerators probe the interactions between quarks and gluons at shorter distances. The understanding of this detailed substructure and of the fundamental forces responsible is one of the keys to unravelling the physics of the structure of matter. This book will be of interest to all theoretical and experimental particle physicists.

From its early beginnings at SLAC in the 1970's, the study of nucleon spin structure using polarized lepton beams and polarized nucleon targets has become increasingly important in nuclear and particle physics, with current experiments at several of the world's high energy and nuclear physics laboratories (CERN, DESY, SLAC and Jefferson Lab) and with enormous related theoretical studies. The understanding of the fascinating but complicated problem of nucleon spin structure has progressed substantially, but fundamental questions remain and it can be confidently predicted that future activity will be high.The Erice Course on The Spin Structure of the Nucleon covered both the experimental and theoretical aspects of the subject, and this volume includes the lectures given at the School. In many cases the lecture material has been extended and updated by the authors. In addition, several recent publications on experimental work have been added in an appendix.

I review quark momentum distributions in the nucleon at large momentum fractions x. Particular attention is paid to the impact of nuclear effects in deuterium on the d/u quark distribution ratio as x -> 1. A new global study of parton distributions, using less restrictive kinematic cuts in Q^2 and W^2, finds strong suppression of the d quark distribution once nuclear corrections are accounted for.

Inclusive electron scattering data are presented for 2H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q2 = 1 to 7 (GeV/c)2. Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable [xi]. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of [xi] opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q2 than previously believed.

This 2001 book examines the motivation for electron scattering and develops the theoretical analysis of the process. It discusses our understanding of the underlying structure of nuclei and nucleons, and summarizes experimental electron scattering capabilities. This title has been reissued as an Open Access publication on Cambridge Core.