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`Current correlators at four loops and heavy quark mass determinations' 

Abstract: The connection between the low energy expansion of the
vacuum polarisation function and the total cross section for hadron
production from e+ e- by low energy sum rules provides a method for
precise determinations of the charm and bottom quark masses. By
combining different techniques to reduce Feynman integrals to master
integrals we calculated the four-loop QCD corrections to the expansion
of the vacuum polarisation up to the third physical coefficient. Using
Pade approximations the full energy dependence can be reconstructed
and further coefficients can be predicted. I will present the results
and discuss their impact on the determinations of the quark masses. 
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