IR-renormalon contribution to the longitudinal structure function FL

The available data on FL suggest the existence of unexpected large higher twist contributions. We use the 1Nf expansion to analyze the renormalon contribution to the coefficient function of the longitudinal structure function FLp−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.