A Gaussian-Sum Filter for Vertex Reconstruction

A vertex reconstruction algorithm was developed based on the Gaussian-sum filter (GSF) and implemented in the framework of the CMS reconstruction program. While linear least-square estimators are optimal in case all observation errors are Gaussian distributed, the GSF offers a better treatment of non-Gaussian distributions of track parameter errors when these are modelled by Gaussian mixtures. In addition, this ensures better protection against outliers and offers some robustness.