Have galactic antiprotons been found in cosmic rays?

Nearly a quarter-century after the first production of antiprotons in the laboratory, a group of experimenters using a balloon-borne superconducting-magnet spectrometer believes they have detected a statistically significant number of these particles in cosmic rays entering the Earth's upper atmosphere. The observation of cosmic-ray antiprotons—believed to be secondary particles, not primordial antimatter from the Big Bang or from antistars—has confirmed theorists' predictions of the ratio of antiprotons to protons in the interstellar medium and has greatly extended the antiproton's measured lifetime. The observation is expected to furnish new information about the amount of matter traversed by the cosmic rays and the mechanism of their acceleration.