Event generation with exponential scaling in multiplicity using AmpliCol

A bstract Efficient generation of LHC events is hindered by the rapidly rising cost of evaluating QCD matrix elements with increasing multiplicity. We build on a recently proposed two-step strategy in which unweighted events are first generated using the leading-colour (LC) approximation and then reweighted to full-colour (FC) accuracy, utilising the LC integration efficiency while recovering the exact FC prediction. In this work we extend the method to general Standard Model processes and present A mpli C ol , a standalone implementation designed for LHC collisions. We benchmark multi-jet, $$ t\overline{t}+\textrm{jets} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>t</mml:mi> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mo>+</mml:mo> <mml:mtext>jets</mml:mtext> </mml:math> , ZZ +jets, and Drell-Yan+jets production, measuring the time required to obtain a fixed number of unweighted events at FC accuracy. Across all processes, the runtime exhibits a stable exponential scaling with multiplicity, far milder than the factorial growth of conventional matrix-element generators. This demonstrates that the A mpli C ol code enables efficient event generation at multiplicities that are otherwise computationally prohibitive.