Fragmentation of the Pb projectile at 158 GeV/nucleon an Pb-Pb interactions

We have investigated the process of fragmentation of the Pb nucleus at 158 GeV/nucleon in Pb-Pb interactions recorded in lead-emulsion chambers of the EMU13 CERN experiment. The number of Pb-Pb interactions found was larger than that expected from the nuclear charge changing cross section which indicates an important role of electromagnetic dissociation processes in Pb-Pb interactions at this high energy. The emission angles of multiply charged projectile fragments as well as of spectator protons were measured using the semiautomated device with the CCD camera mounted on a microscope. Taking the advantage of the unconventional design of the emulsion chambers the charges of all multiply charged projectile fragments were measured. On the basis of these measurements, different modes of the Pb projectile break-up are discussed. The rates and properties of the fragmentation processes such as fission, multifragmentation and disintegration only into singly charged fragments are presented. (author)