학술논문
Cosmic-Ray Proton and Helium Spectra from the First CREAM Flight
Document Type
Working Paper
Author
Yoon, Y. S.; Ahn, H. S.; Allison, P. S.; Bagliesi, M. G.; Beatty, J. J.; Bigongiari, G.; Boyle, P. J.; Childers, J. T.; Conklin, N. B.; Coutu, S.; DuVernois, M. A.; Ganel, O.; Han, J. H.; Jeon, J. A.; Kim, K. C.; Lee, M. H.; Lutz, L.; Maestro, P.; Malinine, A.; Marrocchesi, P. S.; Minnick, S. A.; Mognet, S. I.; Nam, S.; Nutter, S.; Park, I. H.; Park, N. H.; Seo, E. S.; Sina, R.; Swordy, S.; Wakely, S. P.; Wu, J.; Yang, J.; Zei, R.; Zinn, S. Y.
Source
Astrophys.J.728:122,2011
Subject
Language
Abstract
Cosmic-ray proton and helium spectra have been measured with the balloon-borne Cosmic Ray Energetics And Mass experiment flown for 42 days in Antarctica in the 2004-2005 austral summer season. High-energy cosmic-ray data were collected at an average altitude of ~38.5 km with an average atmospheric overburden of ~3.9 g cm$^{-2}$. Individual elements are clearly separated with a charge resolution of ~0.15 e (in charge units) and ~0.2 e for protons and helium nuclei, respectively. The measured spectra at the top of the atmosphere are represented by power laws with a spectral index of -2.66 $\pm$ 0.02 for protons from 2.5 TeV to 250 TeV and -2.58 $\pm$ 0.02 for helium nuclei from 630 GeV/nucleon to 63 TeV/nucleon. They are harder than previous measurements at a few tens of GeV/nucleon. The helium flux is higher than that expected from the extrapolation of the power law fitted to the lower-energy data. The relative abundance of protons to helium nuclei is 9.1 $\pm$ 0.5 for the range from 2.5 TeV/nucleon to 63 TeV/nucleon. This ratio is considerably smaller than the previous measurements at a few tens of GeV/nucleon.
Comment: 20 pages, 4 figures
Comment: 20 pages, 4 figures