Combining higher twist terms with finite order perturbative contributions

Abstract

Higher twist terms, including QCD condensates, are discussed in the context of a finite order perturbative evaluation of the corresponding leading twist terms. It is shown how such higher twist contributions allow one to extend perturbation theory beyond the order where it is normally valid. Higher twist contributions are meaningful if the leading twist term has been calculated to a sufficiently high order. It appears difficult to give meaning to higher twist contributions outside of the procedure for extending the perturbation theory for the leading twist contribution.