Status of the X17 search in Montreal

TL;DR

This paper describes the setup and initial plans for an experiment at Montreal Tandem accelerator to search for the X17 particle via internal pair creation in nuclear decays, with simulations predicting promising detection prospects.

Contribution

It reports the design, setup, and simulation-based prediction for detecting X17 in nuclear decays at Montreal, extending previous searches with new instrumentation and methodology.

Findings

Design and testing of detection hardware completed

Simulations predict clear X17 signal after two weeks of data collection

Potential to extend measurements to other nuclei like $^{10}$B

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 4$\pi$. Preamplifiers and the data acquisition hardware have been designed and tested. The water-cooled $^7$LiF target, mounted on an Al foil 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 $^8$Be. Assuming the ATOMKI evaluation of the electron-pair production rate from X17, a Geant4 simulation predicts observation of a clear signal after about two weeks of data taking with a 2 $\mu$A proton beam. The IPC measurement could eventually be extended to the giant dipole resonance of $^8$Be, as well as to other nuclei, in particular to $^{10}$B.