We find evidence for an infrared fixed point in perturbative QCD using two complementary approximations: The Banks-Zaks expansion and the large-b resummations. Analyzing the $e\sp+e\sp-$ annihilation ratio and the polarized Bjorken-sum-rule of deep-inelastic-scattering, we use the recent calculation of the renormalization-group $\beta$-function to four-loops in QCD to confirm that the Banks-Zaks expansion is relevant when extrapolated from sixteen down to two light quark flavors. We also search for indications of infrared 'freezing' in the Borel-renormalon-inspired 'large-b' resummations. We find the 'large-b' approximation also indicates perturbative 'freezing' of the $e\sp+e\sp-$ annihilation ratio and the polarized Bjorken-sum-rule at leading order. Finally, we study the region, $n\sb{f}$ = 2, where the 'large-$n\sb{f}$' resummation and Banks-Zaks expansion complement one another. We conclude that there is strong evidence for the existence of a perturbative infrared fixed point in the Standard Model QCD.
Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/17158 |
Date | January 1998 |
Creators | Caveny, Scott Andrew |
Contributors | Stevenson, Paul M. |
Source Sets | Rice University |
Language | English |
Detected Language | English |
Type | Thesis, Text |
Format | 96 p., application/pdf |
Page generated in 0.0017 seconds