Soft corrections to inclusive DIS at four loops and beyond
Abstract
We study the threshold corrections to the structure functions in deep-inelastic scattering (DIS) at the fifth logarithmic (N4LL) order of the soft-gluon exponentiation in massless perturbative QCD. Using recent results for the splitting functions and the quark form factor, we derive the fourth-order contribution to the coefficient f q of the form factor and from it the N4LL part of the exponentiation coefficient B DIS in the limit of a large number of colours. An approximation scheme is shown that leads to sufficiently accurate N4LL results for full QCD. The N4LL corrections are small and lead to a further stabilization of the perturbative expansion for the soft-gluon exponent.
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