Multi-scale improved predictions for pp→ tt̄W ⁺+X

A bstract We compare standard fixed-order NLO QCD predictions for the full off-shell pp→ e⁺νₑμ ⁻ν ̄μτ ⁺ντbb ̄(j)+X processes in the multi-lepton decay channel with the results obtained using the M i NLO approach. The M i NLO method, now also implemented in the H elac -NLO framework, provides a dynamic determination of the renormalization and factorization scale settings by identifying the most likely branching histories of the additional jets through an inverse k T -clustering algorithm. The inclusion of Sudakov form factors accounts for the large logarithms that arise in the presence of widely separated scales. We perform a dedicated comparison of the two approaches at both the integrated and differential (fiducial) cross-section levels for the LHC Run II energy of √s=13 TeV. Finally, we present the merging of the full off-shell predictions for pp→ e⁺νₑμ ⁻ν ̄μτ ⁺ντbb ̄+X , pp→ e⁺νₑμ ⁻ν ̄μτ ⁺ντbb ̄j+X and pp→ e⁺νₑμ ⁻ν ̄μτ ⁺ντbb ̄jj , with the aim of improving the description of the underlying pp→ e⁺νₑμ ⁻ν ̄μτ ⁺ντbb ̄+X process.