A New Limit on the Flux of Cosmic Antihelium
T. Saeki, K. Anraku, S. Orito, J. Ormes, M. Imori, B. Kimbell, Y. Makida, H. Matsumoto, H. Matsunaga, J. Mitchell, M. Motoki, J. Nishimura, M. Nozaki, M. Otoba, T. Sanuki, R. Streitmatter, J. Suzuki, K. Tanaka, I. Ueda, N. Yajima, T. Yamagami, A. Yamamoto, T. Yoshida, K. Yoshimura
Abstract
A very sensitive search for cosmic-ray antihelium was performed using data obtained from three scientific flights of 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) m**(-2)sr**(-1)s**(-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 Hebar/He flux ratio is 3.1*10**(-6), 30 times more stringent than the limits obtained in similar rigidity regions with magnetic spectrometers previous to BESS.
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