Performance of the LHCb Vertex Locator

The LHCb experiment at the Large Hadron Collider (LHC) at CERN is a dedicated experiment designed to search for New Physics in the decays of beauty and charm hadrons. These hadrons are identified via their flight distance in the Vertex Locator (VELO), making the VELO extremely important for the physics performance of LHCb. The VELO is a silicon strip detector, located around the interaction region. It consists of two retractable halves with 21 modules each, which are open during injection and closed when ´stable beams´ are declared, bringing the VELO sensors at a distance of 8 mm from the LHC beams. Each module has two n-on-n type silicon sensors mounted back to back. Due to its proximity to the beam it is subject to high doses of radiation, which are non-uniform across the sensors and along the z-axis. The VELO has been operated successfully during the first two years of data taking. Results for the hit resolution, primary vertex resolution and impact parameter resolution are presented. Some aspects of radiation damage are also discussed.