Resolving electrons from protons in ATIC

J. Chang, Purple Mountain Observatory Chinese Academy of Sciences
J. H. Adams, NASA Marshall Space Flight Center
H. S. Ahn, University of Maryland, College Park
G. L. Bashindzhagyan, Lomonosov Moscow State University
K. E. Batkov, Lomonosov Moscow State University
M. Christl, NASA Marshall Space Flight Center
A. R. Fazely, Southern University and A&M College
O. Ganel, University of Maryland, College Park
R. M. Gunashingha, Southern University and A&M College
T. G. Guzik, Louisiana State University
J. Isbert, Louisiana State University
K. C. Kim, University of Maryland, College Park
E. N. Kouznetsov, Lomonosov Moscow State University
Z. W. Lin, The University of Alabama in Huntsville
M. I. Panasyuk, Lomonosov Moscow State University
A. D. Panov, Lomonosov Moscow State University
W. K.H. Schmidt, Max Planck Institute for Solar System Research
E. S. Seo, University of Maryland, College Park
N. V. Sokolskaya, Lomonosov Moscow State University
John W. Watts, NASA Marshall Space Flight Center
J. P. Wefel, Louisiana State University
J. Wu, Louisiana State University
V. I. Zatsepin, Lomonosov Moscow State University


The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed for high energy cosmic ray ion detection. The possibility to identify high energy primary cosmic ray electrons in the presence of the 'background' of cosmic ray protons has been studied by simulating nuclear-electromagnetic cascade showers using the FLUKA Monte Carlo simulation code. The ATIC design, consisting of a graphite target and an energy detection device, a totally active calorimeter built up of 2.5 cm × 2.5 cm × 25.0 cm BGO scintillator bars, gives sufficient information to distinguish electrons from protons. While identifying about 80% of electrons as such, only about 2 in 10,000 protons (@ 150 GeV) will mimic electrons. In September of 1999 ATIC was exposed to high-energy electron and proton beams at the CERN H2 beam line, and this data confirmed the electron detection capabilities of ATIC. From 2000-12-28 to 2001-01-13 ATIC was flown as a long duration balloon test flight from McMurdo, Antarctica, recording over 360 h of data and allowing electron separation to be confirmed in the flight data. In addition, ATIC electron detection capabilities can be checked by atmospheric gamma-ray observations. © 2007 COSPAR.