Observation of transition radiation from relativistic heavy nuclei.

Abstract

We have made the first observation of transition radiation produced by relativistic heavy nuclei. The instrument used in this work is a large cosmic-ray detector for the space shuttle designed to measure the energy spectra of heavy nuclei in the cosmic radiation at TeV/nucleon energies. The response of the detector scales with the charge $Z$ of the primary nucleus as expected from theory. The relative fluctuations in detected transition radiation from heavy nuclei are much smaller than those from singly charged particles, because of the large number of photons produced. This makes possible an accurate determination of the energy of the nucleus in the TeV/nucleon region by measurement of the transition radiation yield. The response of such a detector can be well extrapolated from accelerator measurements with singly charged particles.