Threshold resummation of the structure function F L

Abstract

The behaviour of the quark coefficient function for the longitudinal structure function F L in deep-inelastic scattering is investigated for large values of the Bjorken variable x. We combine a highly plausible conjecture on the large-x limit of the physical evolution kernel for this quantity with our explicit three-loop results to derive the coefficients of the three leading large-x logarithms, α snln 2n-1-k(1 - x), k = 1, 2, 3, to all orders in the strong coupling constant α s. Corresponding results are derived for the non-C F part of the gluon coefficient function suppressed by a factor 1 - x, and for the analogous subleading (1 - x)ln k(1 - x) contributions in the quark case. Our results appear to indicate an obstacle for an exponentiation with a higher logarithmic accuracy. © SISSA 2009.