Gluon distributions and fits using dipole cross sections

I investigate the relationship between the gluon distribution obtained using a dipole model fit to low-$x$ data on ${F}_{2}(x,{Q}^{2})$ and standard gluons obtained from global fits with the collinear factorization theorem at fixed order. I stress the necessity to do fits of this type carefully, and, in particular, to include the contribution from heavy flavors to the inclusive structure function. I find that the dipole cross section must be rather steeper than the gluon distribution, which at least partially explains why dipole model fits produce dipole cross sections growing quite strongly at small $x$, while DGLAP (Dokshitzer-Gribov-Lipatov-Altarelli-Parisi) based fits have valencelike, or even negative, small-$x$ gluons as inputs. However, I also find that the gluon distributions obtained from the dipole fits are much too small to match onto the conventional DGLAP gluons at high ${Q}^{2}\ensuremath{\sim}50\text{ }\mathrm{Ge}{\mathrm{V}}^{2}$, where the two approaches should coincide. The main reason for this discrepancy is found to be the large approximations made in converting the dipole cross sections into structure functions using formulas which are designed only for asymptotically small $x$. The shortcomings in this step affect the accuracy of the extracted dipole cross sections in terms of size and shape, and hence also in terms of interpretation, at all scales.