McMule -- a Monte Carlo generator for low energy processes

TL;DR

McMule is a Monte Carlo generator designed for low-energy lepton processes, now capable of NNLO event generation with improved handling of negative weights, enhancing predictions for experiments like MUonE and MUSE.

Contribution

It introduces NNLO event generation with cellular resampling in McMule, enabling more accurate and efficient low-energy lepton process simulations.

Findings

Supports multiple QED processes at NNLO including mass effects

Can generate events directly at NNLO, not just distributions

Reduces negative event weights through cellular resampling

Abstract

McMule, a Monte Carlo for MUons and other LEptons, implements many major QED processes at NNLO (eg. $ee\to ee$, $e\mu\to e\mu$, $ee\to\mu\mu$, $\ell p\to\ell p$, $\mu\to\nu\bar\nu e$) including effects from the lepton masses, making it suitable for predictions for low-energy experiments such as MUonE, CMD-III, PRad, or MUSE. Recently, McMule gained the ability to generate events at NNLO rather than just pre-defined differential distributions. To avoid negative event weights, it employs cellular resampling directly as part of the generation step which further reduces the fraction of negative weights.