Reevaluation of the hadronic contribution to α(MZ2)

We reevaluate the hadronic part of the electromagnetic vacuum expectation value using the standard dispersion integral approach that utilizes the hadronic cross section measured in ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ experiments as input. Previous analyses are based upon point-by-point trapezoidal integration which does not treat experimental errors in an optimal way. We use a technique that weights the experimental inputs by their stated uncertainties, includes correlations, and incorporates some refinements. We find the five-flavor hadronic contribution to the fractional change in the electromagnetic coupling constant at ${\mathit{q}}^2$=${\mathit{M}}_{\mathit{Z}}^2$, Δα(${\mathit{M}}_{\mathit{Z}}^2$), to be 0.027 52±0.000 46, which leads to a value of the electromagnetic coupling constant, ${\mathrm{\alpha }}^{\mathrm{-}1}$(${\mathit{M}}_{\mathit{Z}}^2$)=128.96±0.06. © 1996 The American Physical Society.