Charmed Hadron Asymmetries in the Intrinsic Charm Coalescence Model

Abstract

Fermilab experiment E791, measuring charmed hadron production in $\pi^- A$ interactions at 500 GeV with high statistics, has observed a strong asymmetry between the hadroproduction cross sections for leading $D$ mesons which contain projectile valence quarks and the nonleading charmed mesons without projectile valence quarks. Such correlations of the charge of the $D$ meson with the quantum numbers of the beam hadron explicitly contradict the factorization theorem in perturbative QCD which predicts that heavy quarks hadronize through a jet fragmentation function that is independent of the initial state. The E791 experiment also measures $\Lambda_c/ \bar \Lambda_c$ and $D_s/\bar{D_s}$ production asymmetries as well as asymmetries in $D \bar D$ pair production. We examine these asymmetries and the fractional longitudinal momentum, $x_F$, distributions for single and pairs of charmed hadrons within a two-component model combining leading-twist $g g$ and $q \bar q$ fusion subprocesses with charm production from intrinsic heavy quark Fock states. A key feature of this analysis is intrinsic charm coalescence, the process by which a charmed quark in the projectile's Fock state wavefunction forms charmed hadrons by combining with valence quarks of similar rapidities.