Usage of CAD Applications as an Open-Use Geometry Modeling Research Software in Particle Physics Experiments

Modern Particle Physics experiments require very complex scientific facilities to perform measurements. Detector technologies based on state-of-the-art achievements and detectors themselves are represented as unique and complex assemblies. Geometrical Descriptions of Detectors (GDD) constitute data widely used in experiments. Various Software Applications (SA) at different phases of experiments use GDD as input data: in engineering phase – Construction/Installation SA, in physics analyses phase – Simulation/Reconstruction SA, and in Outreach – Augmented-reality/Education SA. Our case study of GDD development in ATLAS experiment at LHC (Large Hadron Collider) at CERN shows implementation of heterogeneous approach for GDD development. Each SA uses a separate and unique GDD, and there is no inheritance between GDDs. As a result, several negative trends are observed:  Huge resources in terms of highly qualified expertise are required, including groups of experts employed for a long term  GDDs are sometimes non-synchronized and may lack accuracy, which may cause problems for physics analyses. Differences between theoretical GDDs and actual geometry may cause discrepancies between data and simulations  GDDs are hard to update These problems can be solved by implementation of Inherited Geometry Modelling (IGM) approach, which envisages existence of a central GDD, so-called Reference Geometry (RG). Thus, instead of creating individual GDDs for a SA, they can be derived from the RG. That will solve the problem of synchronization and updates. In addition, the need of high-qualified expertise for specialized GDD development will be reduced. Computer Aided Design (CAD) geometry models are most suitable data for the IGM approach and RG development. Therefore, new requirements apply to CAD applications themselves when they become an important platform in GDD development life cycle in particle physics experiments. Modern CAD applications have open-use architectures, which enables their customization through the third-party programming approach. Thus, custom applications can be developed and run inside CAD application by using all the basic functionality of the parent. This paper discusses a case of GDD development in the ATLAS experiment. CATIA CAD application was customized and integrated into the GDD development loop for simulation and reconstruction tasks. Added functionalities allow considering CATIA as a hub for collecting all GDDs used by Simulation/Reconstruction SAs and export GDDs from the central description into local software applications. The paper describes details of the RG development concept and Simulation/Reconstruction loop based on CATIA.