Abstract:In this article we discuss the calculation of single top-quark production in the t channel at two-loop order in QCD. In particular we present the decomposition of the amplitude according to its spin and colour structure and present complete results for the two-loop amplitudes in terms of master integrals. For the vertex corrections compact analytic expressions are given. The box contributions are implemented in a publicly available C program.
We describe a new, convenient, recursive tensor integral reduction scheme for one-loop n-point Feynman integrals. The reduction is based on the algebraic Davydychev-Tarasov formalism where the tensors are represented by scalars with shifted dimensions and indices, and then expressed by conventional scalars with generalized recurrence relations. The scheme is worked out explicitly for up to n = 6 external legs and for tensor ranks R ≤ n. The tensors are represented by scalar one-to four-point functions in d dimensions. For the evaluation of them, the Fortran code for the tensor reductions has to be linked with a package like QCDloop or LoopTools/FF. Typical numerical results are presented.
We describe a new, convenient, recursive tensor integral reduction scheme for one-loop n-point Feynman integrals. The reduction is based on the algebraic Davydychev-Tarasov formalism where the tensors are represented by scalars with shifted dimensions and indices, and then expressed by conventional scalars with generalized recurrence relations. The scheme is worked out explicitly for up to n = 6 external legs and for tensor ranks R ≤ n. The tensors are represented by scalar one-to four-point functions in d dimensions. For the evaluation of them, the Fortran code for the tensor reductions has to be linked with a package like QCDloop or LoopTools/FF. Typical numerical results are presented.
This study is targeted to the NLO corrections of multileg processes, very important for the LHC. Starting from the construction of Feynman diagrams, the analytical reduction of general one-loop integrals to scalar master ones, the calculation of color structures, manipulation of spinor lines and other amplitude constituents and finally phase space point selection are obtained by use of a program producing Fortran code for numerical calculation of one-loop corrections for processes like gg → ttgg.
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