The search for antimatter in cosmic rays

The search for antimatter in the universe is a page in the history of the I offe Physicotechnical Institute (IPTI). Experiments on spacecraft and high- altitude balloons, begun in the 1960s, yielded information on to the presen ce or absence of antimatter stars or galaxies according to evidence arising in explosive processes in these objects. Antiprotons with energies of 2-5 GeV in galactic cosmic rays were observed at the end of the 1970s in balloo n experiments by the Cosmic Spectrometry Laboratory at the IPTI. These stud ies were done using a magnetic spectrometer at altitudes with a residual pr essure of 10 g/cm(2) with a threshold geomagnetic rigidity of 3 GV. High-la titude experiments in the 1980s, yielding the first measurements of the flu x of galactic antiprotons with energies of 0.2-2 GeV, gave some indication of the mechanism by which they are generated. The measured ratios of the fl uxes of antiprotons and protons in the cosmic rays are 2.4(-1.3)(+2.4)x10(- 4) and 6(-5)(+14)x10(-5) at energies of 2-5 and 0.2-2 GeV, respectively. Su bsequent balloon-borne experiments employing magnetic spectrometers by grou ps from the USA and Japan have confirmed the results obtained by the IPTI. Experimental and theoretical work on the search for antiparticles in cosmic rays is summarized and the astrophysical consequences of this research are discussed. Experimental data on the detection of antiparticles in galactic cosmic rays indicate that there are no objects made of antimatter within t he local group of galaxies. (C) 1999 American Institute of Physics. [S1063- 7842(99)02209-6].