Improving colour computations in MadGraph5_aMC@NLO and exploring a $$1/N_c$$ expansion

Abstract

AbstractIn this paper, we present an extension of which is able to evaluate tree-level QCD matrix-elements up to $$2\rightarrow 6$$ 2 → 6 (one more particle than before). To achieve this, we implemented Berends–Giele-like recursion, and re-implemented the way colour is computed such that we can now expand the colour matrix in powers of $$1/N_c$$ 1 / N c and truncate this expansion to a chosen order. For high multiplicity samples, even without truncating the colour matrix, the new implementation offers a speed gain compared to the previous code.