Physics of heavy-quark production in quantum chromodynamics

For very heavy quark masses, QCD predicts that the inclusive hadronic production of heavy quarks is governed by quark and gluon hard-scattering subprocesses. On general grounds, one expects corrections of order μ/$M_Q$, where μ∼300 MeV and $M_Q$ is the heavy-quark mass. At the charm mass scale, such corrections could be important, possibly accounting for the anomalies observed in the nuclear-number dependence, the longitudinal-momentum distributions, and beam-flavor dependence of charm hadroproduction. In this paper we present a general overview of such corrections. In particular, we discuss a ‘‘coalescence’’ correction, which substantially alters the cross section in situations where the heavy quark is known to have a low velocity relative to one or more constituents of the spectator jet. In attractive channels the result is a large enhancement. In inclusive cross sections this final-state-interaction effect is suppressed by only a single power of the heavy-quark mass.