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

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∼MZ2, 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 αlεklogj+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