k-Factorization and Impact Factors at Next-to-leading Level
  We further analyse,at next-to-leading log(s) level,the form of k-factorization and the definition of impact factors previously proposed by one of us,and we generalize them to the case of hard colourless probes. We then calculate the finite one-loop corrections to quark and gluon impact factors and we find them universal,and given by the same K factor which occurs in the soft timelike splitting functions. 
M.Ciafaloni and D.Colferai, (Firenze)