Dr. John Mitchell
NASA/Goddard Sapce Flight Center
Measuring Antimatter over Antarctica
Measuring cosmic-ray antimatter and nuclei with a balloon-borne instrument is scientifically important and rewarding, and can be surprisingly exciting. This talk will describe the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) program and share some of the adventure of ballooning in Antarctica. The US-Japan BESS collaboration uses elementary particle measurements to study the early Universe and provide fundamental data on thespectra of light cosmic-ray elements and isotopes. BESS measures the energy spectra of cosmic-ray antiprotons to investigate possible signatures of dark-matter candidates and searches for heavier antinuclei that might reach Earth from antimatter domains formed during symmetry breaking processes in the early Universe. The apex of the BESS program was reached with the Antarctic flight of BESS-Polar II that returned data on 4.7 billion cosmic-ray events in 24.5 days during the 2007-2008 Austral Summer. The flight was terminated on 21 January 2008 in a remote location approximately 1800 km from the US McMurdo Station. The instrument was disassembled and recovered in 2009-2010 with a 13-day deep-field camp. The scientific motivation for the BESS measurements and the results of the BESS program will be discussed, focusing on data from BESS-Polar II.