Measurement of the p-bar/p ratio using the moon shadow with the L3 detector

Present measurements on the antiproton flux in cosmic rays are limited to momenta below 50 GeV/c. Measurements to set upper limits to the antiproton flux at higher energies, where antiprotons from secondary origin no longer contribute, are of current interest. To set such a limit, the deficit of muons originating from the Moon's direction is measured as a function of the muon momentum threshold with the L3+C detector at LEP, CERN. The observation of the position and shape of such a shadowing effect allows a determination of the electric charge of TeV cosmic rays through the bending of the particles by the Earth's magnetic field. After a description of the experiment, a preliminary result will be reported. (author)