  Previously published CTEQ6 parton distributions adopt the conventional
zero-mass parton scheme; these sets are most appropriate for use with massless
hard-scattering matrix elements commonly found in most physics applications.
For precision observables which are sensitive to charm and bottom quark mass
effects, we provide in this paper an additional CTEQ6HQ parton distribution set
determined in the more general variable flavor number scheme which incorporates
heavy flavor mass effects. The results are obtained by combining these parton
distributions with consistently matched DIS structure functions computed in the
same scheme. We describe the analysis procedure, examine the predominant
features of the new distributions, and compare with previous distributions.
