A multi-detector array has been constructed for the simultaneous measurement
of energy- and angular correlation of electron-positron pairs produced in
internal pair conversion (IPC) of nuclear transitions up to 18 MeV. The
response functions of the individual detectors have been measured with
mono-energetic beams of electrons. Experimental results obtained with 1.6 MeV
protons on targets containing 11B and 19F show clear IPC over a wide
angular range. A comparison with GEANT simulations demonstrates that angular
correlations of e+e− pairs of transitions in the energy range between 6 and
18 MeV can be determined with sufficient resolution and efficiency to search
for deviations from IPC due to the creation and subsequent decay into e+e−
of a hypothetical short-lived neutral boson.Comment: 20 pages, 8 figure