Existing Packages

Linear Collider Detector (LCD) studies have used quite a number of different Monte Carlo detector simulators over the years. These have included Gismo, LCDROOT, LCDG4, LCS, the JUPITER software package, and Mokka. Early, FORTRAN-based packages included SIMDET, SGV and BRAHMS, mainly for studies on the TESLA detector.

Geometry Requirements

To varying degrees, each of these applications has been used for physics and hardware studies. One might ask the perfectly valid question: "Why introduce yet another simulations package?".

The answer is that none of these programs matches the presumed goal of allowing any type of input geometry or readout type. This is a realistic requirement, given the number of detector geometries that will need to be simulated for a future ILC detector program. These geometries include, but are not limited to, various full detector configurations, such as SiD, GLD, TESLA (D09) and others. There are also multiple testbeam configurations, with data taking to start on the first calorimetry testbeam in the summer of 2005. Presumably, there will be further testbeam studies, including ones for the tracker. Not only are there a variety of basic detector setups to study, each of these may have various versions for the study of different types of subdetectors. For instance, the hadron calorimeter component of the testbeam will study different subdetector technologies including scintillator, RPC and GEM, each of which should be simulated in detail.

None of the current applications seems well-suited to the above requirements. Gismo and its kin, LCDG4 and LCS, read a geometry format that is terse but fairly inflexible in the way it is parsed. This system only provides tube-based detectors, with no general provisions for specifying common Geant4 shapes such as trapezoids. Mokka's model allows flexible input of geometric "primary constants" via a MySQL database into C++ drivers, but it does not provide a consistent, low-level data model for consumer applications. JUPITER and Brahms have fixed geometries that are difficult to modify.

SLIC and LCDD

The simulations framework comprised of Simulator for the Linear Collider (SLIC) and its geometry package, Linear Collider Detector Description (LCDD), attempts to cleanly separate the command and control aspects of simulation from the detector description. LCDD provides an XML format for geometry description built on the GDML package, which is, at least nominally, the official format for geometric data interchange within the LHC's LCG computing group. Using LCDD's detector description format, various types of detector geometries, including testbeams and full detectors, can be specified in detail and simulated using a common runtime, providing a consistent platform for the study of physics and detector systemmatics. The rest of this guide will show you how to use these applications to perform these types of studies.