Submitted to the 2001 Internation Cosmic Ray Conference. Proc. 26th ICRC, p1437 (sequential pages, no volume number)
A Monte Carlo simulation for the interaction of cosmic ray nuclei in an emulsion chamber is described. The simulation uses the DTUNUC event generator to handle the high-energy interactions, and GEANT to follow lower-energy products.
Submitted to the 1999 International Cosmic Ray Conference. Session HE 6.4.13. Proc 26th ICRC (Salt Lake City), V 2, p 527-530.
Spot density is commonly used as an indication of shower energy in emulsion chambers. In a system originally developed for JACEE analysis, the optical density of a spot on x-ray film is estimated from macroscopic digital images. The spot's size is used to compensate for the lack of dynamic range obtainable with digital imaging hardware. These densities are compared to manually measured densities.
Submitted to the 1999 International Cosmic Ray Conference. Session HE 5.3.7.
In heavy particle decays found in cosmic ray interactions recorded in the JACEE emulsion chambers, multiple electron pairs were previously reported. These pairs apparently originated from conversions of photons emitted in the decays. It is difficult to explain the overall properties of these decays in terms of known heavy particle decay modes. A recently published compilation of low-energy nuclear data suggests existence of excess electron pairs with invariant mass about 9 MeV/c^2, which may be explained by postulating a new neutral boson decaying into the electron pair. The feasibility of explaining the JACEE electron pairs with this hypothesis is presented.
For the Antarctic Journal of the United States
The galactic cosmic ray spectrum spans a tremendous energy range, obeying one power law below about 10^15 electron-Volts (eV), and another above 10^16 eV. The region of change in between is called the "knee," and suggests a change in the acceleration mechanism. Below the knee, the mechanism is believed to be understood. Less is known above the knee, and more experiments are needed to understand the mechanism. Five Antarctic balloon flights have allowed the Japanese American Cooperative Emulsion Experiment (JACEE) to extend direct measurements toward this critical region.
Published in Astrophysical Journal 502 (1998) 278-283.
Measurements are presented of the cosmic ray hydrogen and helium spectra at energies from 2 to 800 TeV. 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 helium spectra are consistent with power laws over the entire energy range, with integral spectral indices 1.80 (0.04) and 1.68 (+0.04 /-0.06) 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.
Published in Nuc. Phys. B Proc Suppl, 60(3)(1998) pp 83-92.
Very high energy spectra of cosmic ray nuclei from the JACEE balloon experiments are presented. From a total of 12 balloon flights with an exposure factor of about 580 m2 hour the energy spectra of nuclei have been obtained in the energy range from several TeV to 1000 TeV. Proton energy spectrum, extending to several hundred TeV, can be a single-power law. Helium shows a single power law spectrum in the energy range from 2 TeV/n to 200 TeV/n. Other nuclei up to Fe indicated harder spectral indices compared with those of protons and helium. The composition at around 500 TeV is 16±5%:29±5%:35±5%:9±3%:11±4%, for the abundance of p:He:C-O:Ne-S:Z18.
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