Next-to-leading mass singularities in two-loop electroweak singlet form factors

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We consider virtual electroweak corrections to the form factors for massless chiral fermions coupling to an SU(2)xU(1) singlet gauge boson in the asymptotic region s≫ MW², where the invariant mass s of the external gauge boson is much higher than the weak-boson mass scale. Using the sector-decomposition method we compute mass singularities, which arise as logarithms of s/MW² and 1/ε poles in D=4-2ε dimensions, to one- and two-loop next-to-leading logarithmic accuracy. In this approximation we include all contributions of order αˡ εᵏ logʲ⁺ᵏ(s/MW²), with l=1,2 and j=2l,2l-1. We find that the electroweak two-loop leading- and next-to-leading-logarithmic mass singularities can be written in a form that corresponds to a generalization of Catani's formula for massless QCD.