Measurement of electron capture from electron-positron pair production in relativistic heavy ion collisions

We have used a novel new spectrometer to make the first observation and measurement of electron capture from e⁺-e^- pair production in relativistic heavy ion collisions. For a 0.96 GeV/nucleon U⁹²⁺ beam the cross section for a Au target is 2.19(0.25) b, and the target Z dependence is Zₜ^2.8±0.25. We also measured the energy and angular distributions of the of the positrons, and for comparison, the cross section for e⁺-e^- pair production without capture is 3.30(0.65) b.