Nucleon Spin Structure

COFFEE_KLATCH · Invited

Abstract

Since discovering the nucleon was a composite structure, much has been learned about how its properties (charge, momentum, etc.) arise from the partons within. There has been significant recent activity to understand both the helicity and transverse spin structure. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory allows unique access to study the spin structure through polarized proton-proton collisions Results from polarized DIS measurements over the past 20 years have shown that the quark spin only contributes $\sim25-30$\% to the nucleon spin, indicating that the remainder comes from the gluon spin and parton orbital angular momentum. Measurements of the double helicity asymmetry $A_{LL}$ in polarized proton collisions at RHIC can access the gluon spin contribution, $\Delta G$. Recent result from the STAR and PHENIX Collaborations have been used in a global analysis of polarized data, and were shown to significantly constrain $\Delta G$. New measurements at RHIC using the parity violating spin asymmetry in W boson production access the flavor dependent sea quark spin contributions. First results show good agreement with expectations based on DIS results. The first large data set is being taken this year. RHIC is also able to study the transverse spin structure of the proton, a field that has seen significant growth in recent years. In this talk, we will present our current understanding of the nucleon spin structure, and the role RHIC has played and will continue to play in expanding it.

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Authors

  • Antony Valentini

    CITA, MIT, Caltech/JPL, Academia Sinica, Dong Hwa Univ., Soochow Univ., Nanticoke High School, UT, Maverick Systems Corp., RIS Corp., LSU, Shimadzu Corp., UNIRIB, ORAU/ORISE, Physics Division, Oak Ridge National Laboratory, Oak Ridge Associated Universities, Los Alamos National Laboratory, University of South Dakota, RIKEN BNL Research Center, University of Wisconsin-Milwaukee, Brown University, University of Maryland, Jet Propulsion Laboratory - California Institute of Technology, Center for Relativistic Astrophysics, Georgia Tech, University of Rochester, University of Idaho, Texas A\&M University, Universit\'e Paris Diderot-Paris 7, Washington University in St. Louis, Harvard-Smithsonian Center for Astrophysics, University of California, Berkeley, Massachusetts Institute of Technology, Rockwell Collins Inc., Northwestern University, N IST, Indiana Unviersity, Harvard University, University of Notre Dame, Fachbereich Theoretische Physik, Institut fur Physik, Karl-Franzens-Universitat Graz, Austria, Instituto de Estructura de la Materia, CSIC, Spain, Physics Department, University of Wisconsin-Barron, Orion Foundation, Physics Dept, University of West Florida, Pensacola, Florida, 32514, TUNL, Duke University, James Madison University, University of New Mexico, Photonics CoE, Idaho State University, Pocatello, ID 83209, Los Alamos National Laboratory, Los Alamos, NM 87545, Argonne National Laboratory, University of Washington, National Institute of Standards and Technology, National Institute of Standards and Technology (and West Virginia University), NRAO, University of Florida, LLNL / NPS, LLNL, UC Berkeley, LLNL/NPS, Univerity of Washington, CNRS-IN2P3, Marseille, FR, CERN and King's College, London UK, Brookhaven National Laboratory, ICTP, Trieste, IT, Fermi National Accelerator Laboratory, University of Wisconsin Milwaukee, Princeton University, North Carolina Central U. (NCCU), Triangle Universities Nuclear Laboratory (TUNL), University of California, Riverside, NSCL/MSU, Triangle Universities Nuclear Laboratory, Duke University, University of North Carolina, Duke University, University of North Carolina at Chapel Hill, Triangle Universities Nuclear Laboratory, KVI Groningen, APS Director of Public Affairs, Perimeter Institute, Caltech, Rutgers, U. Tenn., ORNL, Stanford School of Medicine, Radiation Oncology and Molecular Imaging Program, Stanford Applied Physics Department, Stanford School of Medicine, Radiation Oncology, Boston University, BNL, Rutgers University, Purdue University, Penn. State University, UCSD, Lawrence Livermore National Laboratory, University of Richmond, University of Massachusetts-Lowell, Mississippi State University, University of Tennessee, Argonne National Lab, Florida State University, US Naval Academy, ANL, Univ. of Maryland, Univ. of Massachusetts (Lowell), Univ. of Tennessee, Univ. of Manchester, UK, NBI, Danmark, Mississippi State Univ., Physics Division, Argonne National Laboratory, Argonne, IL 60439, Mississippi State University, Mississippi State, MS 39762, UGC-DAE Consortium for Science Research, Kolkata, India, Department of Physics, University of Notre Dame, Notre Dame, IN 46556, San Jose State University, Pacific Northwest National Laboratory, University of Chicago, Fermilab, Program Director, US LHC Accelerator Research Program (LARP), Montana State University, Department of Astrophysical Sciences, Princeton University, School of Mathematics, University of Southampton, CCT, Louisiana State University, CSIC-IEEC Barcelona, TAPIR, California Institute of Technology, University of Texas at Brownsville, Royal Military College of Canada, California State University, Sacramento, Norfolk State University, Oak Ridge National Laboratory, Utah State University, Executive Producer \& Co-Creator of The Big Bang Theory, University of California, Los Angeles, Cyclotron Institute, Texas A\&M University, Hope College, NSCL, Augustana College, Clemson University