Search for Antideuterons of Cosmic Origin Using the BESS-Polar II Magnetic-Rigidity Spectrometer

Abstract

We searched for antideuterons (d¯'s) in the 4.7×109 cosmic-ray events observed during the BESS-Polar II flight at solar minimum in 2007-2008 but found no candidates. The resulting 95% C.L. upper limit on the d¯ flux is 6.7×10-5 (m2 s sr GeV/n)-1 in an energy range from 0.163 to 1.100 GeV/n. The result has improved by more than a factor of 14 from the upper limit of BESS97, which had a potential comparable to that of BESS-Polar II in the search for cosmic-origin d¯'s and was conducted during the former solar minimum. The upper limit of d¯ flux from BESS-Polar II is the first result achieving the sensitivity to constrain the latest theoretical predictions. © 2024 American Physical Society. American Physical Society.