Fast simulation of the energy depositions in high-granular
detectors is needed for future collider experiments at
ever-increasing luminosities. Generative machine learning (ML)
models have been shown to speed up and augment the traditional
simulation chain in physics analysis. However, the majority of
previous efforts were limited to models relying on fixed, regular
detector readout geometries. A major advancement is the recently
introduced CaloClouds model, a geometry-independent diffusion
model, which generates calorimeter showers as point clouds for the
electromagnetic calorimeter of the envisioned International Large
Detector (ILD).
In this work, we introduce CaloClouds II which features a
number of key improvements. This includes continuous time
score-based modelling, which allows for a 25-step sampling with
comparable fidelity to CaloClouds while yielding a
6× speed-up over Geant4 on a single CPU (5×
over CaloClouds). We further distill the diffusion model
into a consistency model allowing for accurate sampling in a single
step and resulting in a 46× speed-up over Geant4
(37× over CaloClouds). This constitutes the first
application of consistency distillation for the generation of
calorimeter showers.