Dr T. Speer (UNIVERSITY OF ZURICH, SWITZERLAND)
A vertex fit algorithm was developed based on the Gaussian-sum filter (GSF) and implemented in the framework of the CMS reconstruction program. While linear least-squares estimators are optimal in case all observation errors are Gaussian distributed, the GSF offers a better treatment of the non-Gaussian distribution of track parameter errors when these are modeled by Gaussian mixtures. In addition, when using electron tracks reconstructed with an electron-reconstruction Gaussian-sum filter, the full mixture can be used rather than the approximation by a single Gaussian. Properties, results and performance of this filter with simulated data will be shown, and compared to the Kalman filter and to robust filters.