====== TTP98-05 A theory driven analysis of the effective QED coupling at $M_Z$ ======
 
 
   <hidden TTP98-05  A theory driven analysis of the effective QED coupling at $M_Z$ > An evaluation of the effective QED coupling at the scale M_Z is
 presented.  It employs the predictions of perturbative QCD for the 
 cross section of electron positron annihilation into hadrons up to order
 \alpha_s^2, including the full quark mass dependence, and of order
 \alpha_s^3 in the high energy region. This allows to predict the input
 for the dispersion relations over a large part of the integration
 region. The perturbative piece is combined with data for
 the lower energies and the heavy quark thresholds. The result for the
 hadronic contribution to the running of the coupling
 \Delta\alpha^{(5)}_{\rm had}(M_Z^2)= (277.5 \pm 1.7)\times 10^{-4}
 leads to (\alpha(M_Z^2))^{-1}=128.927 \pm 0.023. Compared to previous 
 analyses the uncertainty is thus significantly reduced.
 </hidden>
|**J.H. K\"uhn and M. Steinhauser**  | 
|** Phys. Lett. B 437 425-431 1998  **  |
| {{preprints:1998:ttp98-05.pdf|PDF}} {{preprints:1998:ttp98-05.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/9802241|arXiv]]   |
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