Transition and synchrotron radiation produced by electrons and particle discrimination

Transition radiation from a radiator of 650 lithium foils has been studied in a MWPC filled with a xenon-CO2 mixture for two experimental configurations. With the chamber immediately behind the radiator, particle discriminations comparable to those reported in the literature (90% efficiency for electrons, 10% for hadrons) have been observed. With magnetic bending between the radiator and the xenon chamber typical efficiencies of 87% for electrons and less than 0.4% for hadrons have been measured. The discrimination obtained is at least a factor 20 better than for the more conventional configuration. In the latter case, synchrotron radiation has also been observed. (Auth.)