MC@NLO event generation by reweighting unweighted born events

We propose a computational strategy for NLO + PS simulations in the MC@NLO framework that starts from Born-accurate (LO) events and reweights them to the full MC@NLO S S -event weight, while generating H H -events separately. We validate the approach on two representative LHC processes and compare to direct NLO event generation for both standard MC@NLO and MC@NLO- Δ Δ matching. Employing large folding values in the radiative variables stabilizes the S S -event integral, reduces weight variance, and significantly lowers the fraction of negative weights compared to S S -event generation without folding. At fixed precision, this pipeline has comparable wall-clock times relative to standard S S -event generation and unweighting, with room for further optimisation.