The Cosmic Ray Antiproton Spectrum and a Limit on the Antiproton   Lifetime
  Measurements of the cosmic ray pbar/p ratio are compared to predictions from an inhomogeneous leaky box model of Galactic secondary pbar production combined with an updated heliospheric model that modulates the predicted fluxes measured at the Earth. The heliospheric corrections are crucial for understanding the low-energy part of the spectrum. The pbar production- propagation-modulation model agrees with observations. Adding a finite pbar lifetime to the model, we obtain the limit tau(pbar) > 1.7 Myr (90% C.L.). Restrictions on heliospheric properties and the cutoff of low-energy interstellar cosmic rays are discussed. 
Stephen H. Geer (Fermi National Accelerator Laboratory), Dallas C.   Kennedy (University of Florida)