A new experiment, HERA-B, has been installed to investigate the production of heavy quarks in collisions of the high energy proton beam of HERA with nuclei from a wire taget inside the machine. The heavy c- and b- quarks have masses of 1.5 and 5 proton masses, respectively. Like all quarks they cannot be observed directly, but only in combination with another quark, with which they form the so called mesons. HERA is a 'factory' of these heavy mesons, producing them in large numbers.  
The HERA-B experiment has been installed to study their production and decay. Since the heavy mesons are produced in a heavy background of uninteresting particles, this study demands a large discriminating power of the data taking system.