Small-x resummation and HERA structure function data

We apply our systematic NLO small x resummation of singlet splitting functi ons to the scaling violations of structure functions and compare the result s with data. We develop various theoretical tools which are needed in order to relate resummed parton distributions to measurable structure functions, and we present results from a variety of fits to HERA data for the structu re functions F-2 and F-L using the resummation. The behaviour of the single t splitting functions at small x and fixed Q(2) is effectively parametrized as x(-lambda). We find that, for lambda small or negative, the resummed de scription of scaling violations may be phenomenologically as good as or eve n better than the standard next-to-leading order treatment. However, the be st fit gluon density and value of alpha (s) can be significantly modified b y the resummation. (C) 2001 Published by Elsevier Science B.V.