  We present a novel lepton-nucleus event generator: ACHILLES, A CHIcagoLand
Lepton Event Simulator. The generator factorizes the primary interaction from
the propagation of hadrons in the nucleus, which allows for a great deal of
modularity, facilitating further improvements and interfaces with existing
codes. We validate our generator against high quality electron-carbon
scattering data in the quasielastic regime, including the recent CLAS/e4v
reanalysis of existing data. We find good agreement in both inclusive and
exclusive distributions. By varying the assumptions on the propagation of
knocked out nucleons throughout the nucleus, we estimate a component of
theoretical uncertainties. We also propose novel observables that will allow
for further testing of lepton-nucleus scattering models. ACHILLES is readily
extendable to generate neutrino-nucleus scattering events.
