Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions

Journal Article · Fri Aug 24 00:00:00 EDT 2007 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.99.082001· OSTI ID:21028159

Avakian, Harut; Deur, Alexandre ^[1]; Brodsky, Stanley J ^[2]; Yuan, Feng ^[3]

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1. Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)
2. Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States)
3. RIKEN/BNL Research Center, Building 510A, Brookhaven National Laboratory, Upton, New York 11973 (United States)

We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x){sup 5}log{sup 2}(1-x) in the limit of x{yields}1. Our analysis shows that the ratio of the polarized over unpolarized down quark distributions, {delta}d/d, will still approach 1 in this limit. By comparing with the experimental data, we find that this ratio should cross zero at x{approx_equal}0.75.

• OSTI ID: 21028159
• Journal Information: Physical Review Letters, Vol. 99, Issue 8; Other Information: DOI: 10.1103/PhysRevLett.99.082001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0031-9007
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
D QUARKS
FOCK REPRESENTATION
HELICITY
NUCLEONS
ORBITAL ANGULAR MOMENTUM
QUANTUM CHROMODYNAMICS