QCD and Intrinsic Heavy Quark Predictions for Leading Charm and Beauty Hadroproduction

Recent experiments at Fermilab and CERN have observed a strong asymmetry between the hadroproduction cross sections of leading $D$ mesons, containing projectile valence quarks, and nonleading charmed mesons, without projectile valence quarks. The observed correlations of the $\pi^{\pm} N \to D^\pm X$ cross section with the projectile charge violates the usual assumption that heavy quark jet fragmentation factorizes. We examine the asymmetry between leading and nonleading charm production as a function of $x_f$ and $p_T^2$ assuming a two-component model combining leading-twist fusion subprocesses and charm production from intrinsic heavy quark Fock states. We predict a sizable asymmetry at low $p_T^2$ and high $x_f$ from coalescence of the charm quarks with the comoving spectator quarks of the projectile. An intrinsic $c \overline c$ production cross section of 0.5 $\mu$b is sufficient to explain both the magnitude and kinematic dependence of the asymmetry. In contrast, the charm jet hadronization mechanisms contained in PYTHIA predict a sizeable leading charm asymmetry even at low $x_F.$ The two-component model is extended to predict the asymmetry in $B$ meson production in proton-proton and pion-proton interactions.