Part I - Past Activities

III - Computing Infrastructure, Sim and Recon

A - Infrastructure

For the past 10+ years SLAC has been the lead laboratory in the US for linear collider detector R&D computing effort. We have developed flexible tools to allow simulation and reconstruction of detectors in sufficient detail to allow realistic comparison of the capabilities of detector technologies and associated reconstruction algorithms. An emphasis of the group has been on developing infrastructure to allow physicists from universities and other labs to rapidly get started and contribute to detector R&D.

The SLAC group has taken a leading role in the creation and support of standards to ensure a large degree of interoperability with other detector R&D efforts in Europe and Asia. One component of this approach is the LCIO libraries which provide a fully documented standard format for reading and writing events at the generator level, full simulation level and reconstruction and analysis level. The LCIO libraries support C++, Fortran and Java and have been adopted by all most linear collider detector studies worldwide. The interoperability afforded by the LCIO libraries has been a major contributor to the successful completion of the recent LOI effort in the linear collider community.

There are significant differences in the design of tools for detector R&D compared to typical experiment specific simulation and reconstruction code.

• The tools must allow easy reconfiguration to support different detector geometries and technologies.
• The tools must make it easy to develop new reconstruction algorithms and plug them in to the existing reconstruction infrastructure.
• The tools must be very easy for users to set up and become productive. Typically physicists working on detector R&D do so with only a fraction of their effort, and often new graduate students or post-docs take over the work after one or two years.
• The tools must work on a wide variety of operating systems. Unlike established collaborations which can require collaborators' computing platforms to meet certain standards, detector R&D software must work on whatever computing platforms are available to users.
• The tools must be easy to develop and support using a fraction of the manpower that would be available to an established physics collaboration.

The major tools created to meet these design goals are the SLIC Geant4 based simulation program the org.lcsim reconstruction and analysis tools suite.

SLIC is a C++ program based on Geant4 which supports reading standard event generator level input (stdhep) and generates LCIO output files. Rather than having detector geometry built-in to the code, SLIC reads the detector geometry at runtime from an XML detector description. The detector description is based on the standard GDML geometry format developed at CERN, but extended to allow detector response parameterizations to be specified in the same XML file.

The org.lcsim reconstruction and analysis suite is written in Java and includes the following major components:

• Standard geometry system. Both org.lcsim and SLIC work with a common high level "compact detector description" which makes it easy to adjust detector parameters and ensure consistency between the simulated and reconstructed data.
• Full support for LCIO standards for input and output.
• Fast "parameterized" monte-carlo to support rapid development of analysis algorithms
• Full reconstruction infrastructure including digitization, track finding and reconstruction, cluster finding and PFA analysis framework.
• Analysis tools including jet finding and event shape analysis, and histograming and fitting based on the AIDA library.
• Full event-display based on WIRED integrated with the geometry system.

The org.lcsim reconstruction framework can be run standalone, or integrated with the JAS3 interactive data analysis system. The use of Java for the org.lcsim suite greatly simplified the task of supporting multiple target operating systems, and makes it possible to exploit the superb modern development environments which have been developed in the last decade.

These tools were designed to be easy to use and set up so that barriers for users to get involved with the detector simulation effort are low. For several workshops and conferences in the past we have been able to create CDs containing everything a new user needs to get started with these tools, including install kits for a variety of operating systems, documentation and event samples.

In addition to direct support of these tools the SLAC group has:

• Made available a large collection of standard simulation samples for a variety of event types and standard detector and accelerator configurations.
• Hosted infrastructure shared with related efforts worldwide the including the
  • lcsim.org web site,
  • ILC and SiD related content on the confluence wiki(confluence.slac.stanford.edu) including many detailed tutorials and reference documentation.
  • Discussion forums at forum.linearcollider.org. These are the primary means of providing support to end users who have questions or problems using the software, as well as for discussion between software developers world-wide.
  • CVS repository at cvs.freehep.org and automated continuous build system (hudson). This repository is used to host the LCIO libraries, the core SLIC and org.lcsim software and many user contributed analysis algorithms and tools.

Part II Future Plans

III - Computing Infrastructure, Sim and Recon

Support for infrastructure has stalled since layoffs, in particular ability to respond to user requested enhancements and bug fixes has been very limited. Much of the infrastructure used by the SiD effort is shared with other groups at SLAC and we expect the support for this to be co-ordinated with them.

On going support for getting users started with framework.

Goals:

• LCIOv2 – in collaboration with other LCIO developers.
  • Support more detailed reconstruction output based on experience for LoI studies.
  • Support for more efficient analysis of large data samples, including efficient random access to selected events.
• Update SLIC to use latest GDML standards. Support for more realistic detector mechanics and response modeling.
• Update documentation and tutorials, especially to integrate new reconstruction tools developed for LoI.
• Enhanced geometry system able to handle increasingly detailed detector descriptions. Explore common geometry description with others
• Enhance interoperability with other tools. Work around limitations of Root.
• Update plugins for use with JAS
• Improved plotting, especially for publication quality plots
• Improved documentation on AIDA, especially in the area of fitting, advanced plots.
• Run org.lcsim on many-core CPU's