Vertex reconstruction and track bundling at the LEP collider using robust algorithms

This paper presents the application of a robust estimator to the problem of finding and estimating secondary vertices. After a brief review of the standard Kalman filter and its extension to an M-estimator, both estimators are studied on simulated samples of charm and bottom decays. It is shown that the M-estimator is superior to the Kalman filter. The implementation is shown to work also on real data from the LEP collider.