The Leap Experiment: Another Look at the Cosmic-Ray Low-Energy Antiproton Flux

A balloon-borne instrument for a cosmic-ray antiproton search in the 130–1200 MeV range was launched in August 1987. The LEAP (Low-Energy AntiProton) experiment consisted of the NMSU magnet spectrometer, a time-of-flight detector, and a Cherenkov counter. LEAP gathered 23 hours of data at the top of the atmosphere. Preliminary results of the antiproton/proton ratio indicate a 90% confidence upper limit of 3.2xl0-5 for 130 MeV < Tp < 360 MeV [1]. TP is the proton or antiproton kinetic energy at the top of the atmosphere. The LEAP result at 130–360 MeV agrees well with the results of Ahlen et al. [2], but strongly disagrees with the measurement of Buffington et al. [3].