QCD technology: Light-cone quantization and commensurate scale relations

Journal Article · Mon Nov 22 04:00:00 EST 1999 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.1301659· OSTI ID:21210318

Brodsky, Stanley J ^[1]

---

1. Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States)

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.

• OSTI ID: 21210318
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 494; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
CONFORMAL INVARIANCE
CORRELATIONS
COUPLING
DECAY AMPLITUDES
DEEP INELASTIC SCATTERING
DEGREES OF FREEDOM
EFFECTIVE CHARGE
FORM FACTORS
GLUONS
LEPTON-PROTON INTERACTIONS
LIGHT CONE
MATRIX ELEMENTS
PERTURBATION THEORY
POTENTIALS
PROTONS
QUANTIZATION
QUANTUM CHROMODYNAMICS
QUARKS
RENORMALIZATION
WAVE FUNCTIONS