Search for Cosmic-Ray Antideuterons
  We performed a search for cosmic-ray antideuterons using data collected during four BESS balloon flights from 1997 to 2000. No candidate was found. We derived, for the first time, an upper limit of 1.9E-4 (m^2 s sr GeV/nucleon)^(-1) for the differential flux of cosmic-ray antideuterons, at the 95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the atmosphere. 
H. Fuke, T. Maeno, K. Abe, S. Haino, Y. Makida, S. Matsuda, H.   Matsumoto, J. W. Mitchell, A. A. Moiseev, J. Nishimura, M. ...