On the behaviour of non-singlet structure functions at small x

The resummation of O(αsl+1 ln2l x) terms in the evolution kernels of non-singlet combinations of unpolarized and polarized structure functions is investigated. The agreement with complete calculations up to order αs2 is demonstrated, and the leading small-x contributions to the three-loop non-singlet splitting functions P± are derived. The additional contributions due to the resummed terms are studied numerically for the most important non-singlet structure functions. They are found to be about 1% or smaller in the kinematical regions accessible at present and in the foreseeable future.