Why the proton spin is not due to quarks

Conference · Sun Nov 20 04:00:00 EST 1988 · AIP Conf. Proc.; (United States)

OSTI ID:6188464

Karliner, M

Recent EMC data on the spin-dependent proton structure function suggest that very little of the proton spin is due to the helicity of the quarks inside it. We argue that, at leading order in the 1/N/sub c/ expansion, none of the proton spin would be carried by quarks in the chiral limit where mq = 0. This model-independent result is based on a physical picture of the nucleon as a soliton solution of the effective chiral Lagrangian of large-N/sub c/ QCD. The Skyrme model is then used to estimate quark contribution to the proton spin when chiral symmetry and flavor SU(3) are broken: this contribution turns out to be small, as suggested by the EMC. Next, we discuss the other possible contributions to the proton helicity in the infinite-momentum frame--polarized gluons (..delta..G), and orbital angular momentum (L/sub z/). We argue on general grounds and by explicit example that ..delta..G = 0 and that if the parameters of the chiral Lagrangian are adjusted so that gluons carry /similar to/50% of the proton momentum, most of the orbital angular momentum L/sub z/ is carried by quarks. We mention several experiments to test the EMC results and their interpretation.

• Research Organization: Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309
• OSTI ID: 6188464
• Report Number(s): CONF-8805142-
• Conference Information: Journal Name: AIP Conf. Proc.; (United States) Journal Volume: 176:1
• Country of Publication: United States
• Language: English

Related Subjects

645204 -- High Energy Physics-- Particle Interactions & Properties-Theoretical-- Strong Interactions & Properties
645300* -- High Energy Physics-- Particle Invariance Principles & Symmetries
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANGULAR MOMENTUM
BARYONS
ELEMENTARY PARTICLES
EMC EFFECT
FERMIONS
FIELD THEORIES
FUNCTIONS
HADRONS
HELICITY
LAGRANGIAN FIELD THEORY
LIE GROUPS
NUCLEON-NUCLEON POTENTIAL
NUCLEONS
PARTICLE PROPERTIES
POSTULATED PARTICLES
POTENTIALS
PROTONS
QUANTUM CHROMODYNAMICS
QUANTUM FIELD THEORY
QUARKS
SKYRME POTENTIAL
SPIN
STRUCTURE FUNCTIONS
SU GROUPS
SU-3 GROUPS
SYMMETRY GROUPS