VELO vertexing and tracking algorithms of the LHCb trigger system

LHCb is a dedicated CP violation experiment situated at the Large Hadron Collider (LHC) at CERN. It is designed to detect and reconstruct events in which B hadrons are produced. Its silicon vertex detector, the Vertex Locator (VELO), will provide precise topological information for use in LHCb's second level trigger with the aim of selecting events with high sensitivity to CP violation parameters while reducing the data rates from 40 MHz to 40 kHz. Therefore the VELO must provide fast, robust and precise vertexing and tracking for the LHCb trigger system and is a crucial component of the experiment's trigger strategy. The second level trigger vertexing and tracking algorithms are presented in the context of the LHCb trigger strategy, and results presented in terms of efficiency, background suppression and timing. (c) 2005 Published by Elsevier B.V.