====== TTP06-23 Recent Results on Four-loop Tadpoles ======
 
 
<hidden TTP06-23  Recent Results on Four-loop Tadpoles > The experimental measurable R-ratio can be used to perform a precise
 determination of the charm- and bottom-quark mass with the help of
 theoretical computable expansion coefficients of the vacuum
 polarization function.  The four-loop contributions in perturbative QCD
 to the first two expansion coefficients of the vacuum polarization
 functions are presented.
 </hidden>
|**K.G. Chetyrkin, J.H. K\"uhn and C. Sturm**  | 
|**  Nucl. Phys. (Proc. Suppl.)   B160 230-234 2006  **  |
| {{preprints:2006:ttp06-23.pdf|PDF}} {{preprints:2006:ttp06-23.ps|PostScript}}   |
| |