IR-renormalon contribution to the longitudinal structure function FL

Abstract The available data on F L suggest the existence of unexpected large higher twist contributions. We use the 1 N f expansion to analyze the renormalon contribution to the coefficient function of the longitudinal structure function F L p − n . The renormalon ambiguity is calculated for all moments of the structure function thus allowing to estimate the contribution of “genuine” twist-4 corrections as a function of Bjorken- x . The predictions turn out to be in surprisingly good agreement with the experimental data.