Accelerating Electromagnetic Simulations for the HL-LHC: The G4HepEm Breakthrough

1st October 2025 | Source: CERN-EP

The High-Luminosity Large Hadron Collider (HL-LHC) will push data volumes and detector precision to unprecedented levels — demanding faster and more efficient simulation tools. To meet this challenge, researchers from CERN’s EP-SFT group have developed G4HepEm, a new library designed to accelerate electromagnetic shower simulations within the widely used Geant4 framework.

G4HepEm focuses on the most computationally intensive components of particle-physics simulations — the tracking of electrons, positrons, and photons. By introducing a dedicated transport engine for these species, the library achieves significant performance improvements while maintaining the full physics accuracy required by high-energy experiments. Early benchmarks have demonstrated up to a two-fold speed-up in simplified detector setups, paving the way for faster, large-scale studies at the HL-LHC.

In practical use, ATLAS and CMS have already observed double-digit reductions in simulation time per event, marking a key step toward sustainable and scalable computing for the next generation of particle-physics research. G4HepEm integrates seamlessly with existing workflows and can run on CPU and GPU architectures, making it a versatile bridge toward heterogeneous and energy-efficient computing. Details of this work can be found here.