Abstract
The ratio R(S)=(→hadrons)/σ(→) is calculated to the four-loop level in perturbative QCD. The result differs from a previous calculation and is much smaller. In addition, a new result for the four-loop β function in QED is obtained. This result also disagrees with a previous calculation.
- Received 26 November 1990
DOI:https://doi.org/10.1103/PhysRevLett.66.560
©1991 American Physical Society