We present the results of the tree-level calculation of deep-inelastic leptoproduction, including polarization of target hadron and produced hadron. We also discuss the dependence on transverse momenta of the quarks, which leads to azimuthal asymmetries for the produced hadrons.

In this paper we study the leading-twist cross section for polarized Drell-Yan scattering at measured lepton-pair transverse momentum Q T . W e nd that for a hadron with spin 1=2 the quark content a t t wist-two is described by six distribution functions for each a v or, which depend on both the lightcone momentum fraction x, and the quark transverse momentum k 2 T . These functions have a simple partonic interpretation. The cross sections for both longitudinal and transverse polarizations are expressed in terms of convolution integrals over the distribution functions.

ForewordThe study of the fundamental structure of nuclear matter is a central thrust of physics research in the United States. As indicated in Frontiers of Nuclear Science, the 2007 Nuclear Science Advisory Committee long range plan, consideration of a future Electron-Ion Collider (EIC) is a priority and will likely be a significant focus of discussion at the next long range plan. We are therefore pleased to have supported the ten week program in fall 2010 at the Institute of Nuclear Theory which examined at length the science case for the EIC. This program was a major effort; it attracted the maximum allowable attendance over ten weeks.This report summarizes the current understanding of the physics and articulates important open questions that can be addressed by an EIC. It converges towards a set of "golden" experiments that illustrate both the science reach and the technical demands on such a facility, and thereby establishes a firm ground from which to launch the next phase in preparation for the upcoming long range plan discussions. We thank all the participants in this productive program. In particular, we would like to acknowledge the leadership and dedication of the five co-organizers of the program who are also the co-editors of this report.David Kaplan, Director, National Institute for Nuclear Theory Hugh Montgomery, Director, Thomas Jefferson National Accelerator Facility Steven Vigdor, Associate Lab Director, Brookhaven National Laboratory iii Preface This volume is based on a ten-week program on "Gluons and the quark sea at high energies", which took place at the Institute for Nuclear Theory (INT) in Seattle from September 13 to November 19, 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. Guiding questions were• What are the crucial science issues?• How do they fit within the overall goals for nuclear physics?• Why can't they be addressed adequately at existing facilities?• Will they still be interesting in the 2020's, when a suitable facility might be realized?The program started with a five-day workshop on "Perturbative and Non-Perturbative Aspects of QCD at Collider Energies", which was followed by eight weeks of regular program and a concluding four-day workshop on "The Science Case for an EIC".More than 120 theorists and experimentalists took part in the program over ten weeks. It was only possible to smoothly accommodate such a large number of participants because of the extraordinary efforts of the INT staff, to whom we extend our warm thanks and appreciation. We thank the INT Director, David Kaplan, for his strong support of the program and for covering a significant portion of the costs for printing this volume. We gratefully acknowledge additional financial support provided by BNL and JLab.The program w...

The mass spectrum for orbitally excited dibaryon resonances is predicted under the assumption of two clusters of quarks in a stretched bag. Decay mechanisms, stability, and experimental candidates in the Y = 2, 1, and 0 channels are discussed. Natural explanations are found for, e.g., the 3F3 and 'D, pp resonances, for the shoulder at 2.14 GeV, and the enhancement at 2.25 GeV in the Ap invariant-mass spectrum.

We investigate one-particle semi-inclusive processes in lepton-hadron scattering. In unpolarized scattering order Q -I corrections appear only when transverse momenta are detected. We consider the twist-two and -three matrix elements and calculate the semi-inclusive structure functions in terms of quark correlation functions. We find that a t the twist-three level not only the standard quark distribution and fragmentation function contribute, but also two new transverse "profile functions.'' We discuss the gauge invariance of the hadronic tensor at the twist-three level. The results of our approach are used to calculate expressions for some cross sections for semi-inclusive processes.