Absorptive effects and power corrections in low $x$ DGLAP evolution

Understand

We address a long standing problem concerning the scale behaviour of parton densities in the low $x$, low $Q^2$ domain.

• We emphasize the important role of absorptive corrections at low $x$ and use knowledge of diffractive deep inelastic scattering to exclude the absorptive effect from conventional deep inelastic data.
• In this way we obtain a significantly different low $x$ behaviour of the gluon density, which is now much better described by linear DGLAP evolution.
• Accounting also for a second power correction, which arises from the freezing of $\alpha_s$ at low $Q^2$, leads to an essentially flat behaviour of the low $x$ gluon density.