Cosmic-ray proton and helium spectra: results from the Jacee experiment

K. Asakimori, Kobe Women's Junior College
T. H. Burnett, University of Washington
M. L. Cherry, Louisiana State University
K. Chevli, The University of Alabama in Huntsville
M. J. Christ, NASA Marshall Space Flight Center
S. Dake, Kobe University
J. H. Derrickson, Kochi University
W. F. Fountain, Waseda University
M. Fuki, Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
J. C. Gregory, Okayama University of Science
T. Hayashi, High Energy Accelerator Research Organization, Tsukuba
R. Holynski, Hiroshima University
J. Iwai, The Ohio State University
A. Iyono, Institute for Cosmic Ray Research
J. Johnson, WRQ, Inc.
M. Kodayashi, Computer Horizons, Inc.
J. Lord, Tezukayama University
O. Miyamura, Kobe Women's Junior College
K. H. Moon, University of Washington
B. S. Nilsen, Louisiana State University
H. Ooa, The University of Alabama in Huntsville
T. Ogata, NASA Marshall Space Flight Center
E. D. Olson, Kobe University
T. A. Parnell, Kochi University
F. E. Roberts, Waseda University
K. Sengupta, Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
T. Shina, Okayama University of Science
S. C. Strausz, High Energy Accelerator Research Organization, Tsukuba
T. Sugitate, Hiroshima University
Y. Takahashi, The Ohio State University
T. Tominaga, Institute for Cosmic Ray Research
J. W. Watts, WRQ, Inc.
J. P. Wefel, Computer Horizons, Inc.

Abstract

Measurements of the cosmic-ray hydrogen and helium spectra at energies from 20 to 800 TeV are presented. The experiments were performed on a series of twelve balloon flights, including several long duration Australia to South America and Antarctic circumpolar flights. No clear evidence is seen for a spectral break. Both the hydrogen and the helium spectra are consistent with power laws over the entire energy range, with integral spectral indices 1.80 ± 0.04 and 1.68-0.06+0.04 for the protons and helium, respectively. The results are fully consistent with expectations based on supernova shock acceleration coupled with a "leaky box" model of propagation through the Galaxy. © 1998. The American Astronomical Society. All rights reserved.