Universal properties of the electromagnetic interactions of spin-one systems

Journal Article · Tue Sep 01 00:00:00 EDT 1992 · Physical Review, D (Particles Fields); (United States)

DOI:https://doi.org/10.1103/PhysRevD.46.2141· OSTI ID:7012311

Brodsky, S J ^[1]; Hiller, J R ^[2]

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1. Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States)
2. Department of Physics, University of Minnesota enDuluth, Duluth, Minnesota 55812 (United States)

The dominance of helicity-conserving amplitudes in gauge theory is shown to imply universal ratios for the charge, magnetic, and quadrupole form factors of spin-one bound states: {ital G}{sub {ital C}}({ital Q}{sup 2}):{ital G}{sub {ital M}}({ital Q}{sup 2}):{ital G}{sub {ital Q}}({ital Q}{sup 2})=(1{minus}2/3{eta}):2:{minus}1. These ratios hold at large spacelike or timelike momentum transfer in the case of composite systems such as the {rho} or deuteron in QCD. They are also the ratios predicted for the electromagnetic couplings of the {ital W}{sup {plus minus}} for all {ital Q}{sup 2} in the standard model at the tree level. In the case of the deuteron, the leading-twist perturbative QCD predictions are valid at {ital Q}{sup 2}={vert bar}{ital q}{sup 2}1{much gt}{Lambda}{sub QCD}{ital M{ital d}}, but do not require the kinematical ratio {eta}={ital Q}{sup 2}/4{ital M}{sub {ital d}}{sup 2} to be large. These results provide new all-angle predictions for the leading power behavior of the tensor polarization {ital T}{sub 20}({ital Q}{sup 2},{theta}) and the invariant ratio {ital B}({ital Q}{sup 2})/{ital A}({ital Q}{sup 2}). We also use a generalization of the Drell-Hearn-Gerasimov sum rule to show that the magnetic and quadrupole moments of any composite spin-one system take on the canonical values {mu}={ital e}/{ital M} and {ital Q}={minus}{ital e}/{ital M}{sup 2} in the strong binding limit of the zero bound-state radius or infinite excitation energy. This allows new empirical constraints on the possible internal structure of the {ital Z}{sup 0} and {ital W}{sup {plus minus}} vector bosons. Simple gauge-invariant and -covariant models and null zone theory are used to illustrate these results. Complications that arise when the Breit frame is used for form-factor analyses are also pointed out.

• DOE Contract Number: AC03-76SF00515
• OSTI ID: 7012311
• Journal Information: Physical Review, D (Particles Fields); (United States), Vol. 46:5; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
INTERMEDIATE VECTOR BOSONS
ELECTROMAGNETIC INTERACTIONS
QUANTUM CHROMODYNAMICS
BOUND STATE
COMPOSITE MODELS
COUPLING
DEUTERONS
ELECTRIC MOMENTS
ELECTROMAGNETIC FORM FACTORS
GAUGE INVARIANCE
HELICITY
MAGNETIC MOMENTS
MOMENTUM TRANSFER
PERTURBATION THEORY
QUADRUPOLE MOMENTS
SPIN
STANDARD MODEL
ANGULAR MOMENTUM
BASIC INTERACTIONS
BOSONS
CHARGED PARTICLES
ELEMENTARY PARTICLES
FIELD THEORIES
FORM FACTORS
INTERACTIONS
INTERMEDIATE BOSONS
INVARIANCE PRINCIPLES
MATHEMATICAL MODELS
PARTICLE MODELS
PARTICLE PROPERTIES
QUANTUM FIELD THEORY
UNIFIED GAUGE MODELS
662230* - Quantum Chromodynamics- (1992-)
662390 - Electromagnetic Processes & Properties- (1992-)