Quark and gluon spin-2 form factors to two loops in QCD

Abstract

We present two-loop QCD corrections to the quark form factor from the amplitude G ∗ → qq¯ and the gluon form factor from G ∗ → gg in SU(N) gauge theory with nf light flavours. We use ddimensional regularisation and the results are presented to all orders in ε = d - 4. These form factors can be used to obtain next-to-next-to-leading order QCD corrections to hadronic scattering processes in large extra-dimension model where Kaluza-Klein graviton modes couple to Standard Model fields. We find that the form factors satisfy Sudakov integro-differential equation and the resulting cusp, collinear and soft anomalous dimensions are identical to those of electroweak vector boson and gluon form factors. We establish the universal behaviour of the infrared singularities in accordance with the proposal by Catani.