Origin of the Q2-dependence of the DIS structure functions

摘要

We consider in detail Q~2-dependence of the DIS structure functions. Very often this dependence is claimed to be originated by the Q~2-dependence of the QCD coupling. This leads to the small-x asymptotics of the structure functions with Q~2-dependent intercepts. We demonstrate that the DGLAP parametrization αs = αs(Q~2) is an approximation valid in the region of large x (where 2pq can be approximated by Q~2) only, providing the factorization scale is also large. Outside this region, the DGLAP parametrization fails, so αs should be replaced by an effective coupling which is independent of Q~2 at small x. As a consequence, intercepts of the structure functions are independent of Q~2. Nevertheless, the small-x asymptotics of the structure functions explicitly depend on Q~2, even when the coupling does not depend on it. We also consider the structure functions at small Q~2 and give a comment on power-Q~2 corrections to the structure functions at large and small Q~2.