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preprints:2008:ttp08-28 [2016/03/15 20:38] (current)
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 +====== TTP08-28 The Strong Coupling Constant at Low and High Energies ====== 
 +<hidden TTP08-28 ​ The Strong Coupling Constant at Low and High Energies > Recent results for the 
 + cross section of electron-positron annihilation into hadrons and for the 
 + decay rates of the $Z$ boson and the  $\tau$ lepton into hadrons including 
 + ​corrections of order  $\alpha_s^4$ are reviewed. 
 + The consistency between two values ​ of $\alpha_s$ measured 
 + at vastly different energies constitutes 
 + a striking test of asymptotic freedom and requires the proper matching 
 + ​conditions 
 + at charm and bottom thresholds. 
 + ​Combining the results from $Z$ and $\tau$ decays 
 + leads to $\alpha_s(M_Z)=0.1198 \pm  0.0015$ as one of the most precise and 
 + ​presently only 
 + NNNLO result for the strong coupling constant. We report a recent 
 + ​determination of $\alpha_s$ 
 + which is based on a lattice evaluation of the pseudoscalar correlator for 
 + the charm quarks combined 
 + with continuum perturbation theory. 
 + </​hidden>​ 
 +|**J.H. K&​uuml;​hn** ​ |  
 +|**      Contribution to "​Continuous Advances in QCD, 2008" Minnepolis, USA, May 15 - 18, 2008; to be published in the proceedings **  | 
 +| {{preprints:​2008:​ttp08-28.pdf|PDF}} {{preprints:​2008:​ttp08-28.ps|PostScript}} ​  | 
 +| |