Geant4 electromagnetic physics for Run3 and Phase2 LHC

Abstract

For the new Geant4 series 11.X, the electromagnetic (EM) physics sub-libraries were revised and reorganized in view of requirements for simulation of Phase-2 LHC experiments. EM physics simulation takes a significant fraction of the available CPU during massive production of Monte Carlo events for LHC experiments. We present the recent evolution of Geant4 EM sublibraries for the simulation of gamma, electron, and positron transport. Updates of other components of EM physics are also discussed. These developments are included in the new Geant4 version 11.1 (December 2022). The most important modifications concern the reorganization of the initialization of EM physics and the introduction of alternative tracking software. These modifications affect the CPU efficiency of any simulation, and CPU savings depend on geometry and physics configuration for the concrete experimental setup. We will discuss several methods: gamma general process, Woodcock tracking, transportation with multiple scattering process, alternative tracking manager, and the new G4HepEm library. These developments provide a basis for the implementation of EM particle transport on co-processors and GPU. We also will present very recent updates in physics processes and in configuration of EM physics.