Pontecorvo reactions are rare antinucleon annihilation processes that are forbidden on free nucleons
but allowed on nucleons bound within nuclei. The interest in studying this phenomenon lies in its
potential to provide insights into the annihilation mechanism and, particularly, the short-distance
dynamics between nucleons within the nucleus. Some measurements were performed in the past
at CERN’s Low Energy Antiproton Ring (LEAR) using antiprotons annihilating on a deuterium
target. However, no data exist for targets consisting of three nucleons, such as 3He or 3H. The
measurement of the rate of the process 𝑝bar 3He → 𝑝 + 𝑛 would allow for distinguishing between
different theoretical models whose predictions vary by 1-2 orders of magnitude. The ASACUSA
collaboration is studying the feasibility of performing this measurement at CERN’s ELENA-AD.A
preliminary design of a simple measurement apparatus, utilizing plastic scintillators and degrader
layers, is presented, together with Monte Carlo simulations assessing its efficiency in measuring
the branching ratios of the aforementioned reaction and rejecting background from more probable
typical antiproton annihilations in the target.