Measurement of the Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight over Antarctica.

The energy spectrum of cosmic-ray antiprotons (¯p's) from 0.17 to 3.5 GeV has been measured using 7886 ¯p's detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary ¯p calculations. Cosmologically primary ¯p's have been investigated by comparing measured and calculated p spectra. BESS-Polar II data show no evidence of primary ¯p's from the evaporation of primordial black holes. [ABSTRACT FROM AUTHOR]