QCD Technology: Light-Cone Quantization and Commensurate Scale Relations

Technical Report · Fri Sep 03 04:00:00 EDT 1999

DOI:https://doi.org/10.2172/12479· OSTI ID:12479

Brodsky, Stanley J ^[1]

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1. SLAC

I discuss several theoretical tools which are useful for analyzing perturbative and non-perturbative problems in quantum chromodynamics, including (a) the light-cone Fock expansion, (b) the effective charge {alpha}{sub v}, (c) conformal symmetry, and (d) commensurate scale relations. Light-cone Fock-state wavefunctions encode the properties of a hadron in terms of its fundamental quark and gluon degrees of freedom. Given the proton's light-cone wavefunctions, one can compute not only the quark and gluon distributions measured in deep inelastic lepton-proton scattering, but also the multi-parton correlations which control the distribution of particles in the proton fragmentation region and dynamical higher twist effects. Light-cone wavefunctions also provide a systematic framework for evaluating exclusive hadronic matrix elements, including timelike heavy hadron decay amplitudes and form factors. The {alpha}{sub v} coupling, defined from the QCD heavy quark potential, provides a physical expansion parameter for perturbative QCD with an analytic dependence on the fermion masses which is now known to two-loop order. Conformal symmetry provides a template for QCD predictions, including relations between observables which are present even in a theory which is not scale invariant. Commensurate scale relations are perturbative QCD predictions based on conformal symmetry relating observable to observable at fixed relative scale. Such relations have no renormalization scale or scheme ambiguity.

• Research Organization: Stanford Linear Accelerator Center, Menlo Park, CA (US)
• Sponsoring Organization: USDOE Office of Energy Research (ER) (US)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 12479
• Report Number(s): SLAC-PUB-8240
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
DECAY AMPLITUDES
DEGREES OF FREEDOM
EFFECTIVE CHARGE
FERMIONS
FORM FACTORS
FRAGMENTATION
GLUONS
HADRONS
LIGHT CONE
MATRIX ELEMENTS
PROTONS
QUANTIZATION
QUANTUM CHROMODYNAMICS
QUARKS
RENORMALIZATION
SCATTERING
SYMMETRY