Algorithm and Software Development Group

The Algorithm and Software Group develops algorithms for event reconstruction in particle physics experiments. The algorithms are implemented and validated in the respective software frameworks of the experiments. Group members regularly publish articles in dedicated journals. Many developments have found internation acceptance.

Traditionally the focus of the research is on pattern recognition and statistical methods. In addition, calibration and alignment of tracking detectors are topics studied by group members.

Some developments have found applications in other fields of research, for instance proteomics (clustering of peptides) or Bayesian statistics (auxiliary mixture sampling).

Event reconstruction

The reconstruction of an event proceeds in several steps:

  • A pattern recognition algorithm produces track candidates from the individual detector hits.
  • The track parameters (position, direction, momentum) are estimated by statistical methods.
  • Another pattern recognition algorithm assigns the tracks to vertex candidates.
  • The position of the vertices is estimated.
  • In some cases the vertex estimation is improved by imposing physical constraints such as momentum and energy conservation.

Current research topics

The research focuses on the experiments CMS and Belle. In addition, work has started on event reconstruction at the International Linear Collider (ILC).

Recent topics have been:

  • Development of adaptive methods for track and vertex reconstruction.
  • Development and implementation of non-linear filters for electron reconstruction.
  • Development and implementation of a software toolbox for vertex reconstruction (RAVE).
  • Development and implementation of an alignment algorithm for the CMS Inner Tracker.
  • Development of track finding and track fitting modules for the upgraded Belle-II vertex detector.
  • Development of a program for the optimization of tracking detectors at the ILC.
  • Development of statistical methods for material estimation in tracking detectors.

In addition, group members  are active in the physics analysis of the CMS experiment.


Up to now, group members have contributed to the software of the following experiments:

  • WA6 (SPS, CERN)
  • UA1 (SPS collider, CERN)
  • Belle (KEKB, Japan)
  • ILD (planned)