Alignment of the LHCb vertex detector

LHCb is one of the four main experiments of the LHC project, which will start at CERN in 2007. It will be primarily dedicated to B-Physics analysis. This requires precise vertex reconstruction. This is the role of the Vertex Detector (VELO), which has to fulfill very tight requirements, and this in turn places strict constraints on its alignment. This paper describes the main alignment procedure chosen for the VELO, concentrating particularly on the software alignment.