Here the authors considered a decay channel of a proton decaying into a positive pion and a dark fermion ... other estimates range from 0.7 to as high as 4.2 billion years.

The J/ψ meson subsequently decays into a pair of muons while the K *0 meson is studied through its decay into a charged pion and a charged kaon. The analysis is based on proton–proton collision ...