LHCb VELO software alignment, Part III: the alignment of the relative   sensor positions
  The LHCb Vertex Locator contains 42 silicon sensor modules. Each module has two silicon sensors. A method for determining the relative alignment of the silicon sensors within each module from data is presented. The software implementation details are discussed. Monte-Carlo simulation studies are described that demonstrate an alignment precision of 1.3 micron is obtained in the sensor plane. 
M. Gersabeck, C. Parkes, S. Viret