Spin structure of the nucleon in the asymptotic limit

Journal Article · Mon Jan 01 04:00:00 EST 1996 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.76.740· OSTI ID:282064

Ji, X; Tang, J ^[1]; Hoodbhoy, P ^[1]

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1. Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

In analogy with the Altarelli-Parisi equation for quark and gluon helicity contributions to the nucleon spin, we derive an evolution equation for quark and gluon orbital angular momenta. Solution of the combined equations yields asymptotic fractions of the nucleon spin carried by quarks and gluons: {Delta}{Sigma}/2+{ital L}{sub {ital q}}=3{ital n}{sub {ital f}}/(16+3{ital n}{sub {ital f}}) and {Delta}{ital g}+{ital L}{sub {ital g}}=16/(16+3{ital n}{sub {ital f}}), respectively, with {ital n}{sub {ital f}} the number of active quark flavors. These are identical to the well-known asymptotic partitions of the nucleon momentum between quark and gluon contributions. The axial-anomaly contribution to the quark helicity is canceled with a similar contribution to the quark orbital angular momentum, making the total quark contribution to the nucleon spin anomaly free. {copyright} {ital 1996 The American Physical Society.}

• DOE Contract Number: FC02-94ER40818
• OSTI ID: 282064
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 5 Vol. 76; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ANGULAR MOMENTUM
GLUONS
HELICITY
LORENTZ TRANSFORMATIONS
NUCLEONS
QUANTUM CHROMODYNAMICS
QUARKS
SPIN