QCD perturbative expansion for {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}hadrons
- Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403 (United States)
- Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States)
We study the perturbative QCD series for the hadronic width of the {ital Z} boson. We sum a class of large {open_quote}{open_quote}{pi}{sup 2} terms{close_quote}{close_quote} and reorganize the series so as to minimize {open_quote}{open_quote}renormalon{close_quote}{close_quote} effects. We also consider the renormalization scheme-scale ambiguity of the perturbative results. We find that, with three nontrivial known terms in the perturbative expansion, the treatment of the {pi}{sup 2} terms is quite important, while renormalon effects are less important. The measured hadronic width of the {ital Z} is often used to determine the value of {alpha}{sub {ital s}}({ital M}{sup 2}{sub {ital Z}}). A standard method is to use the perturbative expansion for the width truncated at order {alpha}{sup 3}{sub {ital s}} in the {bar M}{bar S} scheme with scale {mu}={ital M}{sub {ital Z}}. We estimate that the determined value of {alpha}{sub {ital s}}({ital M}{sup 2}{sub {ital Z}}) should be increased by 0.6{percent} compared to the value extracted with this standard method. After this adjustment for {pi}{sup 2} and renormalon effects, we estimate that the uncertainty in {alpha}{sub {ital s}}({ital M}{sup 2}{sub {ital Z}}) arising from QCD theory is about 0.4{percent}. This is, of course, much less than the experimental uncertainty of about 5{percent}. {copyright} {ital 1996 The American Physical Society.}
- DOE Contract Number:
- FG05-84ER40141; FG06-85ER40224
- OSTI ID:
- 389037
- Journal Information:
- Physical Review, D, Vol. 54, Issue 7; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
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