Open charm hadroproduction and perturbative QCD

The authors critically study the method and the validity of perturbative QCD in open-charm hadroproduction. They explain how the gluon-fusion process (G+G to c+c) and the flavor-excitation process (q +c to q+c or G+c to G+c) should be calculated in line with a principle or perturbative QCD (absorption of mass singularities into parton distributions), and without causing double counting. In this framework it is rather unlikely that the cross section of the excitation process is as large as approximately 1 mb at CERN ISR energy \sqrt{s} approximately=60 GeV. The authors discuss how large the cross section can be through possible higher-order effects. The x/sub F/ distribution of charmed hadrons is also analyzed. By using a simple model for the recombination of charm quarks with fast-moving valence quarks, they show that it is easy to explain the observed hard spectrum of charm baryons.