Calibration of the mirror system in the HERA-B RICH

The mirror system of the HERA-B RICH consists of two spherical and two planar mirrors, composed of altogether 116 mirror segments. Analysis of displacements of the \v{C}erenkov ring center relative to the charged particle track, for given spherical-planar segment pairs, leads to accurate information regarding the orientation of individual mirror segments. The method is described and the effect of applying the required corrections on the \v{C}erenkov angle resolution of the HERA-B RICH is discussed.