====== TTP95-26 ANGULAR DISTRIBUTIONS OF MASSIVE QUARKS AND LEPTONS CLOSE TO THRESHOLD  ======
 
 
   <hidden TTP95-26  ANGULAR DISTRIBUTIONS OF MASSIVE QUARKS AND LEPTONS CLOSE TO THRESHOLD  > Predictions for the angular distribution of massive quarks and
 leptons are presented, including QCD and QED corrections. Recent
 results for the fermionic part of the two-loop corrections to the
 electromagnetic form factors are combined with the BLM scale fixing
 prescription. Two distinctly different scales arise as arguments of
 $\alpha_s(\mu^2)$ near threshold: the relative momentum of the
 quarks governing the soft gluon exchange responsible for the Coulomb
 potential, and a large momentum scale approximately equal to twice
 the quark mass for the corrections induced by transverse gluons.
 Numerical predictions for charmed, bottom, and top quarks are given.
 One obtains a direct determination of $\alpha_{\mbox{\it\scriptsize
 V}}(Q^2)$, the coupling in the heavy quark potential, which can be
 compared with lattice gauge theory predictions. The corresponding
 QED results for $\tau$ pair production allow for a measurement of
 the magnetic moment of the $\tau$ and could be tested at a future
 $\tau$-charm factory.
 </hidden>
|**S.J. Brodsky, A.H. Hoang, J.H. K\"uhn and T. Teubner,**  | 
|** Phys. Lett. B359 355-361 1995  **  |
| {{preprints:1995:ttp95-26.pdf|PDF}} {{preprints:1995:ttp95-26.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/9508274|arXiv]]   |
| |