Characteristics of Charm Production by 400-GeV Protons

In a beam-dump experiment at Fermilab the cross section for charm-particle production has been deduced from a measurement of the prompt neutrino flux. The reaction cross section, if we assume only $D\overline{D}$ and the dependence on atomic weight $A^{0.75}$, is 57.2 ± 2.9 ± 8.5 μb/nucleon and the dependence on Feynman $x$ and transverse momentum is $\frac{E_D{d}^3\sigma }{d{p}_D^3}\propto {\mathrm{}(1-x)\mathrm{}}^{3.2}{e}^{-1.5\mathrm{}{p}_{\perp }}$ ($p_{\perp }$ in GeV/c). The data are consistent with as much as 40% diffractive production of ${\Lambda }_c\overline{D}$.