Determining the uncertainty on the total heavy-flavor cross section

Abstract

We assess the theoretical uncertainties on the total heavy-quark cross section. We discuss the importance of the quark mass, the choice of the scale, the number of light flavors and the parton densities on the estimate of the uncertainty. At first glance, the uncertainty bands on the total charm cross sections obtained by integrating the FONLL inclusive cross section and by integrating the partonic total cross sections appear to be incompatible. We explain how this apparent difference arises and describe how the two results can be reconciled. The small mass of the charm quark amplifies the effect of varying the other parameters in the calculation, making the uncertainty on the total charm cross section difficult to quantify. On the other hand, the bottom-quark total cross section is under much better theoretical control, and differences between the two approaches are small.