I discuss a new approach to the evaluation of the top contribution in the NLO virtual QCD corrections in 2 -> 2 gluon-initiated processes. The approach is based on the combination of two different analytic evaluation of the corrections that are valid in complementary regions of the phase space. The first evaluation is based on an expansion in the forward kinematics and covers the phase-space region of low transverse momentum of the outgoing particles while the second one is based on expansion in high energy that covers the complementary region of high transverse momentum. I then present a new Monte Carlo code for Higgs boson pair production at NLO in the POWHEG-BOX framework based on this approach for the evaluation of two-loop virtual corrections. The main feature of this new MC is the freely assignment of all input parameter including the trilinear Higgs boson self coupling. A second application of this approach to Higgs production in association with a Z boson is also presented.
Luca Vecchi