Alignment of the VELO detector on the Z axis using secondary vertexes reconstruction

LHCb is one of the four main experiments at the LHC, designed to perform CP violation measurements and heavy flavor physics. The LHCb Vertex locator (VELO) is used to reconstruct primary and secondary vertexes from collisions with an accuracy of 5-10µm. To deliver said resolution, the position of the VELO must be precisely known. This is provided by a survey and refined using a 3 step track-based software procedure. Said procedure is accurate (O(µm)) for correcting x and y axis misalignments while its efficiency decreases when dealing with the so called “weak modes”. Here a technique for constraining “weak modes”, specifically scalings on z axis, using secondary vertex reconstruction is proposed and analyzed. Results from preliminary studies are presented, showing that the method has a resolution consistent with the one of the standard software procedure. Suggestions for further refinements and studies are given.