2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/177487A sample of kinematically identified $K^+ \to π^+ π^0$ decays obtained with the E949 detector was used to search for the helicity-suppressed decay $π^0 \to ν\barν$ resulting in an upper limit of $2.7\times10^{-7}$ at 90% confidence level.The upper limit is also applicable to $π^0$ decays into unknown weakly interacting particles.9 pages, 3 figures; no change in the results, accepted for publication in Physical Review DHigh Energy Physics - Experimenttext