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I investigate the relationship between the gluon distribution obtained usinga dipole model fit to low-x data on F_2(x,Q^2) and standard gluons obtainedfrom global fits with the collinear factorization theorem at fixed order. Istress the necessity to do fits of this type carefully, and in particular toinclude the contribution from heavy flavours to the inclusive structurefunction. I find that the dipole cross-section must be rather steeper than thegluon distribution, which at least partially explains why dipole model fitsproduce dipole cross-sections growing quite strongly at small x, while DGLAPbased fits have valence-like, or even negative, small-x gluons as inputs.However, I also find that the gluon distributions obtained from the dipole fitsare much too small to match onto the conventional DGLAP gluons at high Q^2,i.e. approx 50 GeV^2, where the two approaches should coincide. The main reasonfor this discrepancy is found to be the large approximations made in convertingthe dipole cross-sections into structure functions using formulae which aredesigned only for asymptotically small x. The shortcomings in this step affectthe accuracy of the extracted dipole cross-sections in terms of size and shape,and hence also in terms of interpretation, at all scales.Comment: 24 pages, 4 figures, uses axodraw.st

Gluon distributions and fits using dipole cross sections