Search for antihelium with the BESS-polar spectrometer

K. Abe, H. Fuke, S. Haino, T. Hams, M. Hasegawa, A. Horikoshi, A. Itazaki, K. C. Kim, T. Kumazawa, A. Kusumoto, M. H. Lee, Y. Makida, S. Matsuda, Y. Matsukawa, K. Matsumoto, J. W. Mitchell, Z. Myers, J. Nishimura, M. Nozaki, R. OritoJ. F. Ormes, K. Sakai, M. Sasaki, E. S. Seo, Y. Shikaze, R. Shinoda, R. E. Streitmatter, J. Suzuki, Y. Takasugi, K. Takeuchi, K. Tanaka, N. Thakur, T. Yamagami, A. Yamamoto, T. Yoshida, K. Yoshimura

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49 Citations (Scopus)


In two long-duration balloon flights over Antarctica, the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) collaboration has searched for antihelium in the cosmic radiation with the highest sensitivity reported. BESS-Polar I flew in 2004, observing for 8.5 days. BESS-Polar II flew in 2007-2008, observing for 24.5 days. No antihelium candidate was found in BESS-Polar I data among 8.4×106 |Z|=2 nuclei from 1.0 to 20 GV or in BESS-Polar II data among 4.0×107 |Z|=2 nuclei from 1.0 to 14 GV. Assuming antihelium to have the same spectral shape as helium, a 95% confidence upper limit to the possible abundance of antihelium relative to helium of 6.9×10 -8 was determined combining all BESS data, including the two BESS-Polar flights. With no assumed antihelium spectrum and a weighted average of the lowest antihelium efficiencies for each flight, an upper limit of 1.0×10 -7 from 1.6 to 14 GV was determined for the combined BESS-Polar data. Under both antihelium spectral assumptions, these are the lowest limits obtained to date.

Original languageEnglish
Article number131301
JournalPhysical Review Letters
Issue number13
Publication statusPublished - Mar 29 2012
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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