Status of the HERA-B experiment

HERA-B is a fixed target experiment using the halo of the 920 GeV proton beam of HERA on an internal wire target. The aim of the experiment is to trigger on rare B to J/ψ decays, using a highly selective trigger system and to measure the CP violating parameter sin(2β). The specific problems of the experiment arise from the extreme background conditions which put unprecedented requirements on the detector components and the triggering and read out system. After 6 years of intense R and D, HERA-B has been finally completed and is now in its commissioning phase. (author)