Search for antimatter with the AMS cosmic ray detector

Abstract

Antimatter search results of the Alpha Magnetic Spectrometer (AMS) detector are presented. About 10 8 triggers were collected in the 1998 precursor flight onboard space shuttle Discovery. This ten day mission exposed the detector on a 51.7° orbit at an altitude around 350km. Identification of charged cosmic rays is achieved by multiple energy loss and time-of-flight measurements. Bending inside the 0.15T magnetic volume yields a measurement of the absolute value of the particle's rigidity. The supplemental knowledge of the sense of traversal identifies the sign of the charge. In the rigidity range 1 < R < 140 GV no antinucleus at any rigidity was detected, while 2.86 × 10 6 helium and 1.65 × 10 5 heavy nuclei were precisely measured. Hence, upper limits on the flux ratio Z/Z are given. Different prior assumptions on the antimatter spectrum are considered and corresponding limits are given.