$\Lambda, \Xi$ and $\Omega$ production in Pb-Pb interactions at 158 A GeV/c

Using LEP1 data taken in 1994 and 1995, the DELPHI collaboration has a preliminary measurement of $Gamma_{b\overline{b}}/\Gamma_{had}$ which was submitted to the Jerusalem HEP'97 conference. Use of the upgraded microvertex detector, installed in spring 1994, together with an improved track search procedure has allowed the development of powerful new b-quark tags. The combination of these tags in a multivariate analysis is presented with particular emphasis on new features of the method compared to DELPHI publications on earlier data sets.