Soft gluon effects in the extraction of higher twists at large Bjorken x

Existing data on the (unpolarised) transverse structure function of the proton are analyzed for large values of the Bjorken variable x. The leading-twist and a phenomenological higher-twist contributions are simultaneously determined from a power correction analysis of the Nachtmann moments for values of the squared four-momentum transfer between ~ 1 and 20 (GeV/c)**2. The results obtained adopting the next-to-leading order approximation and those including the effects of soft gluon resummation are compared. The sensitivity of the extraction of large-x higher twists to high-order radiative corrections as well as to the value of a_s(M_Z) is illustrated