Conveners
NNLO QCD corrections to t\bar{t}W production in the leading-colour approximation
- Matteo Becchetti
Description
In this talk, I will discuss the calculation of NNLO QCD corrections for the production of a top-antitop quark pair in association with a W boson at the LHC. The two-loop scattering amplitudes entering the double-virtual contribution are calculated in the leading-colour limit without any kinematic approximation, retaining the exact dependence on the masses of the top quark and the W boson. The calculation involves a high degree of algebraic complexity and non-trivial analytic structures in the underlying Feynman integrals, including nested square roots and elliptic integrals.
In order to address such difficulties we employ an hybrid approach. We express the amplitude in terms of a set of special functions, which we evaluate numerically by solving the associated system of differential equations, while the rational coefficients of the special functions are computed numerically through finite fields techniques. Finally, the corresponding two-loop hard function are evaluated on a grid of phase-space points in order to obtain the NNLO QCD cross section through interpolation.