Disentangling running coupling and conformal effects in QCD
We investigate the relation between a postulated skeleton expansion and the conformal limit of QCD. We begin by developing some consequences of an Abelian-like skeleton expansion, which allows one to disentangle running-coupling effects from the remaining skeleton coefficients. The latter are by construction renormalon free, and hence hopefully better behaved. We consider a simple ansatz for the expansion, where an observable is written as a sum of integrals over the running coupling. We show that in this framework one can set a unique Brodsky-Lepage-Mackenzie (BLM) scale-setting procedure as an approximation to the running-coupling integrals, where the BLM coefficients coincide with the skeleton ones. Alternatively, the running-coupling integrals can be approximated using the effective charge method. We discuss the limitations in disentangling running coupling effects in the absence of a diagrammatic construction of the skeleton expansion. Independently of the assumed skeleton structure we show that BLM coefficients coincide with conformal coefficients defined in the small {beta}{sub 0} (Banks-Zaks) limit where a perturbative infrared fixed point is present. This interpretation of the BLM coefficients should explain their previously observed simplicity and smallness. Numerical examples are critically discussed.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40205117
- Journal Information:
- Physical Review D, Vol. 63, Issue 9; Other Information: DOI: 10.1103/PhysRevD.63.094017; Othernumber: PRVDAQ000063000009094017000001; 025109PRD; PBD: 1 May 2001; ISSN 0556-2821
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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