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Volume 301 - 35th International Cosmic Ray Conference (ICRC2017) - Session Cosmic-Ray Direct. CRD- direct measurements
Measurement of the Cosmic-ray Antiproton spectrum in the range 0.12 to 0.4 GeV with BESS-Polar II
K. Sakai,* K. Abe, H. Fuke, S. Haino, T. Hams, M. Hasegawa, K.C. Kim, M.H. Lee, Y. Makida, J.W. Mitchell, J. Nishimura, M. Nozaki, R. Orito, J.F. Ormes, N. Picot-Clemente, M. Sasaki, E.S. Seo, R.E. Streitmatter, J. Suzuki, K. Tanaka, N. Thakur, A. Yamamoto, T. Yoshida, K. Yoshimura
*corresponding author
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Pre-published on: 2017 August 16
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The energy spectra of cosmic-ray antiprotons and protons near solar minimum were precisely measured with BESS-Polar II (Balloon-borne Experiment with a Superconducting Spectrometer) during a long-duration flight over Antarctica in December 2007 and January 2008. The upper-TOF (UTOF) and lower-TOF (LTOF) scintillator hodoscopes measure the charge and velocity of incident particles. A thin plastic scintillator middle-TOF (MTOF) hodoscope is installed on the lower surface of the magnet bore to measure low-energy particles that cannot reach the LTOF. The MTOF further lowers the threshold energy to about 120 MeV for antiproton or proton measurements. We report absolute spectra of the cosmic-ray antiproton in the range 0.12 to 0.4 GeV and the antiproton/proton ratio calculated with UTOF-MTOF trigger events. These new results are independent of the UTOF-LTOF triggered antiproton spectrum published in 2012 and proton
spectrum published in 2016.
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