Heavy-flavor PDF evolution and variable-flavor number scheme uncertainties in deep-inelastic scattering

We consider a detailed account on the construction of the heavy-quark parton distribution functions for charm and bottom, starting from n${}_f$=3 light flavors in the fixed-flavor number (FFN) scheme and by using the standard decoupling relations for heavy quarks in QCD. We also account for two-mass effects. Furthermore, different implementations of the variable-flavor-number (VFN) scheme in deep-inelastic scattering (DIS) are studied, with the particular focus on the resummation of large logarithms in Q${}^2$/m${}_h^2$, the ratio the virtuality of the exchanged gauge-boson Q${}^2$ to the heavy-quark mass squared m${}_h^2$. A little impact of resummation effects if found in the kinematic range of the existing data on the DIS charm-quark production so that they can be described very well within the FFN scheme. Finally, we study the theoretical uncertainties associated to the VFN scheme, which manifest predominantly at small Q${}^2$.