SPIN AND ORBITAL ANGULAR MOMENTUM IN THE PROTON

THOMAS, ANTHONY W.

doi:10.1142/s0218301309013403

SPIN AND ORBITAL ANGULAR MOMENTUM IN THE PROTON

Conference · Mon Jun 01 04:00:00 EDT 2009 · International Journal of Modern Physics E

DOI:https://doi.org/10.1142/s0218301309013403· OSTI ID:2001501

THOMAS, ANTHONY W. ^[1]

Jefferson Lab, Newport News VA 23606, USA; College of William and Mary, Williamsburg VA 23187, USA

Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data.

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Research Organization:: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Nuclear Physics (NP)

DOE Contract Number:: AC05-06OR23177

OSTI ID:: 2001501

Report Number(s):: JLAB-THY-08-818; arXiv:0904.1735; DOE/OR/23177-0677

Conference Information:: Journal Name: International Journal of Modern Physics E Journal Issue: 05n06 Journal Volume: 18

Country of Publication:: United States

Language:: English

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