Status of the LHCb VErtex LOcator

LHCb is a single arm spectrometer at the LHC. It is dedicated to the study of CP violation in the B-hadron system. The VErtex LOcator (VELO) is a silicon microstrip detector providing accurate measurements of event primary and secondary vertices, impact parameters, and tracks. The second level trigger decision of LHCb is mainly based on information from a full readout of the VELO. This document gives a general introduction to LHCb as a context for a more extensive description of the VELO. The VELO design emphasises the need for precise reconstruction of tracks down to momenta of a few GeV. The VELO operates inside the LHC beam-pipe, and the sensors, the hybrids, and the foil separating the primary and secondary vacuua must be built with the minimum possible material. The R-$\phi$ strip layout is optimised for efficient trigger operation and precise measurements at the smallest radii. The performance must be maintained in the harsh radiation environment close to the LHC beams. These issues have led to a choice of n-on-n, double metal technology for the VELO. This document describes the current status of the VELO design, incorporating changes which have been made in the context of the recent overall optimisation of the LHCb detector (``LHCb light'')~\cite{bib:lhcblight}, and summarises the underlying R\&D for the technology choice. Issues concerning the electronics, the mechanical integration into LHCb and the LHC machine are discussed in detail elsewhere~\cite{bib:tdr}.