mb from ALEPH and comparison with other LEP experiments

Abstract

I will review the measurements of the $b$-quark mass performed by ALEPH and DELPHI. A large set of observables has been used together with detailed studies on jet algorithms. Very clear effects due to the $b$-quark mass running are observed. Comparing with the determinations at the $\Upsilon(4S)$ threshold, the measurements of the running $b$-quark mass at the $Z$ pole are consistent with the predicted evolution from QCD.