@article{0812034a6fbb48e491fbdbdb8a99b4fb,
title = "A new limit on the flux of cosmic antihelium",
abstract = "A very sensitive search for cosmic-ray antihelium was performed using data obtained from three scientific flights of the BESS magnetic rigidity spectrometer. We have not observed any antihelium; this places a model-independent upper limit (95% C.L.) on the antihelium flux of 6 × 10-4 m2sr-1S-1 at the top of the atmosphere in the rigidity region 1 to 16 GV, after correcting for the estimated interaction loss of antihelium in the air and in the instrument. The corresponding upper limit on the He/He flux ratio is 3.1 × 106, 30 times more stringent than the limits obtained in similar rigidity regions with magnetic spectrometers previous to BESS.",
keywords = "Antihelium, Antimatter, Cosmic-ray, Universe",
author = "T. Saeki and K. Anraku and S. Orito and J. Ormes and M. Imori and B. Kimbell and Y. Makida and H. Matsumoto and H. Matsunaga and J. Mitchell and M. Motoki and J. Nishimura and M. Nozaki and M. Otoba and T. Sanuki and R. Streitmatter and J. Suzuki and K. Tanaka and I. Ueda and N. Yajima and T. Yamagami and A. Yamamoto and T. Yoshida and K. Yoshimura",
note = "Funding Information: The resultant 95% C.L. upper limit on the /He flux ratio at TOA is 3.1×10 −6 in the rigidity region from 1 to 16 GV. The upper limit on the antihelium flux integrated over the rigidity region is 6×10 −4 m −2 sr −1 s −1 . It should be noted that these upper limits are very conservative and are valid for any hypothetical antihelium spectrum. The limit on the flux ratio obtained by this work is shown in Fig. 5 together with the previous ones [2, 15] . Our flux ratio is a factor 7 improvement over the limit of Buffington et al. who looked for the annihilation signal of low rigidity (1–2 GV) antihelium in a spark chamber calorimeter, and is 30 times more stringent than the limit of Golden et al. who covered a rigidity region similar to ours by using a previous generation magnetic rigidity spectrometer. The large acceptance of BESS, which is designed [16] specially for the antimatter and antiproton searches, made it possible to set this limit.The contributions of late R. Golden is deeply acknowledged. The authors thank NASA/GSFC/WFF Balloon office and NSBF for the balloon expeditions, and KEK and ISAS for various supports. Sincere thanks are given to Y. Ajima, Y. Higashi and D. Righter for their help with the flights and recovery, and to A. Moiseev for discussions. This experiment was supported by NASA in the USA, and by Grant-in-Aid for Scientific Research and for International Scientific Research from the Ministry of Education, by the Kurata Research Grant, and by Sumitomo Research Grant in Japan. The analysis was performed on the RS/6000 workstations supplied for the partnership program between ICEPP and IBM Japan, Ltd.",
year = "1998",
month = mar,
day = "12",
doi = "10.1016/S0370-2693(98)00131-2",
language = "English",
volume = "422",
pages = "319--324",
journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",
issn = "0370-2693",
publisher = "Elsevier",
number = "1-4",
}