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We review the determination of the QED coupling at the Z pole, which is acrucial parameter for electroweak theory. We include recent e+e- -> hadron datafrom Novosibirsk and Beijing to re-evaluate alpha (M_Z^2). We find 1/alpha(M_Z^2) = 128.973 +/- 0.035 or 128.934 +/- 0.040 according, respectively, towhether inclusive or exclusive e+e- -> hadron data are used in the interval 1.4< \sqrt{s} < 2.1 GeV. The error is mainly due to uncertainties in the data inthe low energy region, \sqrt{s} < 2.5 GeV. We find that no advantage isobtained by analytic continuation of the dispersion relation into the complex splane. We show that the hints of structure for \sqrt{s} ~ 2.5 GeV may beevidence of a non-perturbative gluonic contribution to R(s).Comment: LaTeX, 7 pages, 2 eps figures, proceedings of the UK Phenomenology Workshop on Collider Physics, 19-24 September, Durham 1999, contribution to be published in J. Phys.

journal of physics. g, nuclear and particle physics

TheRratio in e+e-, the determination of α (MZ2) and a possible non-perturbative gluonic contribution