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We consider one-loop scalar and tensor integrals with an arbitrary number of external legs relevant for multi-parton processes in massless theories. We present a procedure to reduce N-point scalar functions with generic 4-dimensional external momenta to box integrals in (4 − 2ǫ) dimensions. We derive a formula valid for arbitrary N and give an explicit(More)
We discuss the production of photon pairs in hadronic collisions, from fixed target to LHC energies. The study which follows is based on a QCD calculation at full next-to-leading order accuracy, including single and double fragmentation contributions, and implemented in the form of a general purpose computer program of " partonic event generator " type. To(More)
We describe a constructive procedure to separate overlapping infrared divergences in multi– loop integrals. Working with a parametric representation in D = 4 − 2ǫ dimensions, adequate subtractions lead to a Laurent series in ǫ, where the coefficients of the pole– and finite terms are sums of regular parameter integrals which can be evaluated numerically. We(More)
We present a formalism for the calculation of multi-particle one-loop amplitudes, valid for an arbitrary number N of external legs, and for massive as well as massless particles. A new method for the tensor reduction is suggested which naturally isolates infrared divergences by construction. We prove that for N ≥ 5, higher dimensional integrals can be(More)
We calculate the order O(α 2 α 3 s) interference effect between the gluon fusion and weak boson fusion processes allowed at the one-loop level in Higgs boson plus 2 jet production at the LHC. The corresponding one-loop amplitudes, which have not been considered in the literature so far, are evaluated analytically using dimensional regularisation and the(More)
We derive the six-photon scattering amplitudes for all helicity configurations, obtaining compact analytical expressions. Two recently developed methods, based on form factor decomposition and on multiple cuts are used for this calculation. The self-interaction of photons (light-by-light scattering) mediated through a virtual charged fermion loop is a(More)