Recursive generation of one-loop amplitudes in the Standard Model

Abstract

We introduce the computer code Recola for the recursive generation of tree-level and one-loop amplitudes in the Standard Model. Tree-level amplitudes are constructed using off-shell currents instead of Feynman diagrams as basic building blocks. One-loop amplitudes are represented as linear combinations of tensor integrals whose coefficients are calculated similarly to the tree-level amplitudes by recursive construction of loop off-shell currents. We introduce a novel algorithm for the treatment of colour, assigning a colour structure to each off-shell current which enables us to recursively construct the colour structure of the amplitude efficiently. Recola is interfaced with a tensor-integral library and provides complete one-loop Standard Model amplitudes including rational terms and counterterms. As a first application we consider Z+2jets production at the LHC and calculate with Recola the next-to-leading-order electroweak corrections to the dominant partonic channels.

Comments: 25 pages, 8 eps figures, section on accuracy and efficiency added, version to appear in JHEP