The Virtual Geometry Model

The Virtual Geometry Model (VGM) is a geometry conversion tool, providing conversion between Geant4 and ROOT TGeo geometry models. Its design allows inclusion of another geometry model by implementing a single sub-module instead of writing bilateral converters for all already supported models. In this presentation we will give an update on the tool architecture, implementation and supported features, the user examples, testing and documentation. We will discuss the opportunities for using the tool for verification of the user geometries. Finally, we will also present the tool build system, distribution and releases policy

New Developments in the VMC Project

International audienceVirtual Monte Carlo (VMC) provides a unified interface to different detector simulation transport engines such as GEANT3 and GEANT4. Since recently all the VMC packages (the VMC core library, also included in ROOT, and the GEANT3 and GEANT4 VMC) are distributed via the VMC Project GitHub organization. In addition to these VMC related packages, the VMC project also includes the Virtual Geometry Model (VGM), which is optionally used in GEANT4 VMC for conversion between GEANT4 and ROOT TGeo geometry models.In this contribution we will present the new organization of the VMC project at GitHub and new developments in the VMC interfaces and the VMC packages. We will cover the introduction of the sensitive detector interface in the VMC core and both GEANT3 and GEANT4 VMC and the new GEANT4-related developments.GEANT4 VMC 3.0 with the integration of multithreading processing was presented at CHEP in 2015. In this presentation we will report on new features included since this version: the improved support for magnetic fields, the integration of fast simulation, Garfield physics, GEANT4 transition radiation and monopole physics. Five new VMC examples demonstrating these new features, and serving also for tests, will be also discussed. Finally we will mention the work towards the code quality and improvements in testing, documentation and automated code formatting

Analysis Tools in Geant4

International audienceThe analysis category was introduced in Geant4 more than ten years ago (in 2011) with the aim to provide users with a lightweight analysis tool, available as part of the Geant4 installation without the need to link to an external analysis package. It helps capture statistical data in the form of histograms and n-tuples and store these in files in four various formats. It was already presented at CHEP multiple times, the last time five years ago. In this article we give an update on its evolution since then.We will report on new functionalities: the connection of the analysis to visualization, flexibility in the selection of the output files and also saving data in multiple formats from the same simulation run, and new support for data object cycles in the latest version Geant4 11.1.We will then present the evolution of its design including the major update in the past two years that allowed the introduction of a new Generic analysis manager. In particular, we will discuss the advantages of our design choice based on the so-called Non Virtual Interface pattern: the code robustness and stability in the context of the code evolution over more than ten years.Finally, we will present the continuous code improvements using static code analysis and sanitizer tools

Using multiple engines in the Virtual Monte Carlo package

The Virtual Monte Carlo (VMC) package provides a unified interface to different detector simulation transport engines such as GEANT3 and GEANT4. It has been in production use in various experiments but so far the simulation of one event was restricted to the usage of a single chosen engine. We introduce here the possibility to mix multiple engines within the simulation of a single event. Depending on user conditions the simulation is partitioned among the chosen engines, for instance to profit from each of their advantages or specific capabilities. Such conditions can depend on phase space, geometry, particle type or an arbitrary combination. As a main achievement, this development allows for the implementation of fast simulation kernels at the VMC level which can be used stand-alone or together with full simulation engines. This capability is crucial to cope with largely increasing data expected in future LHC runs

Using multiple engines in the Virtual Monte Carlo package

International audienceThe Virtual Monte Carlo (VMC) package provides a unified interface to different detector simulation transport engines such as GEANT3 and GEANT4. It has been in production use in various experiments but so far the simulation of one event was restricted to the usage of a single chosen engine. We introduce here the possibility to mix multiple engines within the simulation of a single event. Depending on user conditions the simulation is partitioned among the chosen engines, for instance to profit from each of their advantages or specific capabilities. Such conditions can depend on phase space, geometry, particle type or an arbitrary combination.As a main achievement, this development allows for the implementation of fast simulation kernels at the VMC level which can be used stand-alone or together with full simulation engines. This capability is crucial to cope with largely increasing data expected in future LHC runs

A Geant4/Garfield++ and Geant4/Degrad Interface for the Simulation of Gaseous Detectors

For several years, attempts have been made to interface Geant4 and other software packages with the aim of simulating the complete response of a gaseous particle detector. The present paper illustrates different possibilities to interface Geant4 with two such packages, Garfield++ and Degrad. The basic idea is to use the Geant4 physics parameterization feature and to implement a Garfield++ or Degrad based detector simulation as an external model. With the Geant4/Degrad interface, detailed simulations of the X-ray interaction in gaseous detectors, including shell absorption by photoelectric effect, subsequent Auger shake-off, and fluorescence emission, become possible. The Geant4/Garfield++ interface can be used for photons and charged particles of all kinetic energies. Depending on the particular physics case, either the Geant4 PAI model, the Heed PAI model or both Geant4 and Heed are responsible for primary ionization and the production of the conduction electrons. For the case in which the Geant4 PAI model is used in conjunction with the Heed PAI model, a more detailed analysis is performed. Parameters, such as the lower production cut of the PAI model and the lowest electron energy limit of the physics list have to be set correctly. The paper demonstrates how to determine these parameters with the help of the W value and Fano factor of the gas mixture. The simulation results of this Geant4/Heed PAI model interface are then verified against the results obtained with the standalone software packages

Interfacing Geant4, Garfield++ and Degrad for the Simulation of Gaseous Detectors

International audienceFor several years, attempts have been made to interface Geant4 and other software packages with the aim of simulating the complete response of a gaseous particle detector. In such a simulation, Geant4 is always responsible for the primary particle generation and the interactions that occur in the non-gaseous detector material. Garfield++ on the other hand always deals with the drift of ions and electrons, amplification via electron avalanches and finally signal generation. For the ionizing interaction of particles with the gas, different options and physics models exist. The present paper focuses on how to use Geant4, Garfield++ (including its Heed and SRIM interfaces) and Degrad to create the electron–ion pairs stemming from the ionization of the gas. Software-wise, the proposed idea is to use the Geant4 physics parameterization feature, and to implement a Garfield++ or Degrad based detector simulation as an external model. With a Degrad model, detailed simulations of the X-ray interaction in gaseous detectors, including shell absorption by photoelectric effect, subsequent Auger cascade, shake-off and fluorescence emission, become possible. A simple Garfield++ model can be used for photons (Heed), heavy ions (SRIM) and relativistic charged particles or MIPs (Heed). For non-relativistic charged particles, more effort is required, and a combined Geant4/Garfield++ model must be used. This model, the Geant4/Heed PAI model interface, uses the Geant4 PAI model in conjunction with the Heed PAI model. Parameters, such as the lower production cut of the Geant4 PAI model and the lowest electron energy limit of the physics list have to be set correctly. The paper demonstrates how to determine these parameters for certain values of the W parameter and Fano factor of the gas mixture. The simulation results of this Geant4/Heed PAI model interface are then verified against the results obtained with the stand-alone software packages

Geant4 electromagnetic physics progress

The Geant4 electromagnetic (EM) physics sub-packages are a component of LHC experiment simulations. During long shutdown 2 for LHC, these packages are under intensive development and we report progress of EM physics in Geant4 versions 10.5 and 10.6, which includes faster computation, more accurate EM models, and extensions to the validation suite. New approaches are developed to simulate radiation damage for silicon vertex detectors and for configuration of multiple scattering per detector region. Improvements in user interfaces developed for low-energy and the Geant4-DNA project are used also for LHC simulation optimisation

Geant4 electromagnetic physics progress

The Geant4 electromagnetic (EM) physics sub-packages are a component of LHC experiment simulations. During long shutdown 2 for LHC, these packages are under intensive development and we report progress of EM physics in Geant4 versions 10.5 and 10.6, which includes faster computation, more accurate EM models, and extensions to the validation suite. New approaches are developed to simulate radiation damage for silicon vertex detectors and for configuration of multiple scattering per detector region. Improvements in user interfaces developed for low-energy and the Geant4-DNA project are used also for LHC simulation optimisation

Geant4 electromagnetic physics progress

The Geant4 electromagnetic (EM) physics sub-packages are a component of LHC experiment simulations. During long shutdown 2 for LHC, these packages are under intensive development and we report progress of EM physics in Geant4 versions 10.5 and 10.6, which includes faster computation, more accurate EM models, and extensions to the validation suite. New approaches are developed to simulate radiation damage for silicon vertex detectors and for configuration of multiple scattering per detector region. Improvements in user interfaces developed for low-energy and the Geant4-DNA project are used also for LHC simulation optimisation