Study of spectral moments in semileptonic decays of the b hadron with the DELPHI detector at LEP

The measurement of the moments of hadronic mass spectrum and of lepton energy spectrum based on a sample of semileptonic decays of the b hadron selected from $Z^0 \to b \bar b$ events recorded with the DELPHI detector at LEP, are presented. These results are interpreted in terms of constraints on the quark masses and on the b-quark kinetic energy value.