Morphing parton showers with event derivatives

Abstract

We develop EventMover, a differentiable parton shower event generator. This tool generates high- and variable-length scattering events that can be moved with simulation derivatives to change the value of the scale $\Lambda_\mathrm{QCD}$ defining the strong coupling constant, without introducing statistical variations between samples. To demonstrate the potential for EventMover, we compare the output of the simulation with $e^+e^-$ data to show how one could fit $\Lambda_\mathrm{QCD}$ with only a single event sample. This is a critical step towards a fully differentiable event generator for particle and nuclear physics.