Feynman-x and Transverse Momentum Dependence of D Meson Production in 250 GeV pi, K, and p Interactions with Nuclei

Leading-particle effect from heavy-quark recombination

The leading particle effect in charm hadroproduction is an enhancement of the cross section for a charmed hadron D in the forward direction of the beam when the beam hadron has a valence parton in common with the D. The large D(+)/D(-) asymmetry observed by the E791 experiment is an example of this phenomenon. We show that the heavy-quark recombination mechanism provides an economical expla-nation for this effect. In particular, the D(+)/D(-) asymmetry can be fit reasonably well using a single parameter whose value is consistent with a recent determination from charm photoproduction.

Does the D(-)/D(+) production asymmetry decrease at large x(F)?

We have applied the meson cloud model to calculate the asymmetries in D and D(s) meson production in high-energy Sigma(-)-nucleus and pi(-)-nucleus collisions. We find a good agreement with recent data. Our results suggest that the asymmetries may decrease at large x(F).