Atomic mass dependence ofD±andD0,D¯0production in 250 GeVπ±-nucleon interactions

We measure the relative cross sections for D mesons produced in interactions of ${\mathrm{\pi }}^{\mathrm{-}}$ and ${\mathrm{\pi }}^{+}$ beams with targets of Be, Cu, Al, and W. The measurement is based on 1400 fully reconstructed decays of the types ${\mathit{D}}^0$→${\mathit{K}}^{\mathrm{-}}$ ${\mathrm{\pi }}^{+}$, ${\mathit{D}}^{+}$→${\mathit{K}}^{\mathrm{-}}$ ${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{+}$, and charge conjugates. We find that the cross section for the production of both neutral and charged D’s by either ${\mathrm{\pi }}^{\mathrm{-}}$ or ${\mathrm{\pi }}^{+}$ is well fitted by the form ${\mathit{A}}^{\mathrm{\alpha }}$ where A is the atomic mass and α=1.00±0.05±0.02, where the errors are statistical and systematic, respectively. There is no significant dependence of α on the transverse or longitudinal momentum of the D meson or on the charge of either the incident pion or the produced D mesons.