Search for Antimatter with the AMS Cosmic Ray Detector

Antimatter search results of the Alpha Magnetic Spectrometer (AMS) detector are presented. About 100 million triggers were collected in the 1998 precursor flight onboard space shuttle Discovery. This ten day mission exposed the detector on a 51.7 degrees orbit at an altitude around 350 km. Identification of charged cosmic rays is achieved by multiple energy loss and time-of-flight measurements. Bending inside the 0.15 T 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 million helium and 165 thousand heavy nuclei were precisely measured. Hence, upper limits on the flux ratio antinuclei-to-nuclei are given. Different prior assumptions on the antimatter spectrum are considered and corresponding limits are given.