  The results of analysis SERP-E-184 experiment data, obtained with 70 GeV
proton beam irradiation of active target with carbon, silicon and lead plates
are presented. For 3-prongs charged charmed mesons decays, event selection
criteria were developed and detection efficiency was calculated with detailed
simulation using FRITIOF7.02 and GEANT3.21 programs. Signals of decays were
found and charm production inclusive cross sections estimated at near threshold
energy. The lifetimes and A-dependence of cross section were measured. Yields
of D mesons and their ratios in comparison with data of other experiments and
theoretical predictions are presented.
