John Apostolakis (CERN)
The Geant4 toolkit is used in the production detector simulations of most recent High Energy Physics experiments, and diverse applications in medical physics, radiation estimation for satellite electronics and other fields. We report on key improvements relevant to HEP applications that were provided in the most recent releases: 9.6 (Dec 2012) and 10.0 (Dec 2013). 'Strong' reproducibility of events is a requirement of LHC experiments: the same results (hit data) must be obtained when restarting a job from an intermediate event. A significant extension of testing and several corrections in releases 9.6 and 10.0 achieve this for most applications. Multithreading(MT) is included in release 10.0 for parallelism at the event level. It can harness the computing power of multicore machines scalably, with a small increase in memory footprint per additional thread. We report on performance and memory size measurements for release 10.0 on multi-core CPUs and on Xeon Phi (™). Strong reproducibility is required for repeatability of results when using multithreading (MT). Release 10.0 contains the first version of 'USolids', a common library of shape primitives being developed to replace both Geant4 and Root implementations. The USolid implementations for many solids are an option at installation. Field propagation is extended to particles with dipole moments coupling to a magnetic field gradient. There is a new option to turn on gravity, which used to require a user's own code. Geant4 9.6 includes the new INCL 5.1 cascade, reengineered and written in C++ for reactions of pions and nuclei (H-alpha) up to 3 GeV. Release 10.0 introduces tracking of long-lived meta-stable nuclides (isomers), and isomer production in the de-excitation models and radioactive decay. A new improved neutron capture model and revised neutron cross sections below 20 MeV are used in production physics lists (rel. 10.0). These improve simulations that cannot afford the higher CPU cost of the detailed NeutronHP package. Results for tungsten calorimeters, are brought close to those of NeutronHP. Many other improvements and refinements were made in other physics models. The Bertini-inspired cascade was extended to provide gamma- and electro-nuclear interactions and the capture at rest of negative hadrons and muons. The phase-space generation for multi-body states and the two-body final state angular distributions were improved. Development of the FTF string model includes the extension to handle nucleus-nucleus collisions and improved diffraction dissociation of protons, pions and kaons. In addition the LEP and HEP parameterised physics models (inherited from GHEISHA and refined) and the CHIPS models have been retired and removed from release 10.0.
John Apostolakis (CERN)
Dr Alberto Ribon (CERN) Andrea Dotti (SLAC National Accelerator Laboratory (US)) Dennis Herbert Wright (SLAC National Accelerator Laboratory (US)) Dr Gabriele Cosmo (CERN) Gunter Folger (CERN) Dr Makoto Asai (SLAC National Accelerator Laboratory (US)) Dr Marc Verderi (Ecole Polytechnique (FR)) Marek Gayer (CERN) Michael Kelsey (SLAC National Accelerator Laboratory (US)) Tatiana Nikitina (Gangneung-Wonju National University (KR)) Dr Tatsumi Koi (SLAC National Accelerator Laboratory (US)) Prof. Vladimir Ivantchenko (CERN) Vladimir Uzhinskiy (Joint Inst. for Nuclear Research (RU)) Witold Pokorski (CERN)