Evolution of forward multi-particle spectrometers at storage rings

We review the evolution of forward multi-particle spectrometers at storage rings. The first such spectrometers at a proton-proton colliding beam machine were Experiments R603 and R608 which ran at the CERN ISR during 1973–1974 and 1980–1983, respectively. A microvertex detector capability was developed at CERN in the P238 test-experiment at the SPS-Collider in 1990. LHC-B is a third-generation version planned for the CERN Large Hadron Collider, which will be dedicated to the study of CP violation in B-meson decays and other rare phenomena. Other experiments, in which a stored beam interacts with an (internal) fixed target, were Experiment UA6 at the SPS-Collider (gas-jet target) during 1984–1990 and, under construction at DESY, the HERA-B experiment at the HERA proton storage ring, which will run with wire targets in the proton beam halo.