A novel factorization for $F_L$ in the large $x$ limit

Abstract

A novel factorization formula is presented for the longitudinal structure function $F_L$ near the elastic region $x \to 1$ of deeply inelastic scattering. In moment space this formula can resum all contributions to $F_L$ that are of order $\ln^k N/N$. This is achieved by defining a new jet function which probes the transverse momentum of the struck parton in the target at leading twist. The anomalous dimension $\gamma_{J^\prime}$ of this new jet operator generates in moment space the logarithmic enhancements coming from the fragmentation of the current jet in the final state. It is also shown how the suggested factorization for $F_L$ is related to the corresponding one for $F_2$ in the same kinematic region.