Status of the X17 search in Montreal

Abstract

At the Montreal Tandem accelerator, an experiment is being set up to measure internal pair creation from the decay of nuclear excited states using a multiwire proportional chamber and scintillator bars surrounding it from the Daphne experiment. The acceptance covers a solid angle of nearly 4π. Preamplifiers and the data acquisition hardware have been designed and tested. The 7LiF target, mounted on an Al foil and water-cooled is in a thin carbon fiber section of the beamline. The experiment will focus at first on a measurement of the internal pair creation from the 18.15 MeV state of 8Be with the aim of observing independently the X17 particle discovered by the ATOMKI experiment. Assuming the ATOMKI evaluation of the electron-pair production rate from X17, Geant4 simulation predicts observation of a clear signal after about 2 weeks of data taking with 2 μA proton beam. The IPC measurement could eventually be extended to the giant dipole resonance of 8Be, as well as to other nuclei, in particular to 10B.