A new limit on the antiproton lifetime

Measurements of the cosmic-ray;(p) over bar/p ratio are compared with predi ctions from an inhomogeneous disk-diffusion model of (p) over bar productio n and propagation within the Galaxy, combined with a calculation of the mod ulation of the interstellar cosmic-ray spectra as the particles propagate t hrough the heliosphere to the Earth. The predictions agree with the observe d (p) over bar/p spectrum. Adding a finite p lifetime to the model, we obta in the limit tau((p) over bar) > 0.8 Myr (90% CL).