1pm - 2pm: ESME stays positive: event generation with positive weights

The presence of negative event weights in beyond-leading-order event generators significantly reduce the statistical efficiency of Monte Carlo simulations and complicate their use in experimental analyses, and so are best to be avoided. ESME is a new positive-definite matching scheme for NLO event generation. The method has recently been implemented in the PanScales framework, demonstrating fast NLO+NLL event generation for a selection of colour-singlet processes. In this talk, we present the key theoretical and algorithmic principles underlying the construction of ESME, highlighting features that are broadly applicable to other Monte Carlo event generators. We then describe its concrete implementation within PanScales, focusing on its interplay with NLL-accurate parton showers and the mechanisms by which full NLO+NLL accuracy is achieved.