Institute for Theoretical Particle Physics (TTP)

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preprints:1995:ttp95-26 [2016/03/17 11:03] (current)
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 +====== TTP95-26 ANGULAR DISTRIBUTIONS OF MASSIVE QUARKS AND LEPTONS CLOSE TO THRESHOLD  ====== 
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 +   <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]]   | 
 +| |