  We present a leading order QCD analysis of a sample of neutrino induced
charged-current events with two muons in the final state originating in the
lead-scintillating fibre calorimeter of the CHORUS detector. The results are
based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign
dimuon events collected during the exposure of the detector to the CERN Wide
Band Neutrino Beam between 1995 and 1998. % with $E_{\mu 1},E_{\mu 2} > 5$ GeV
and $Q^2 > 3$ GeV$^2$ collected %between 1995 and 1998. The analysis yields a
value of the charm quark mass of $\mc = (1.26\pm 0.16 \pm 0.09) \GeVcc $ and a
value of the ratio of the strange to non-strange sea in the nucleon of $\kappa
= 0.33 \pm 0.05 \pm 0.05$, improving the results obtained in similar analyses
by previous experiments.
