Energy spectra of H and He from the ATIC-2 experiment

J. P. Wefel, Louisiana State University
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
J. Chang, Max Plank Institute for Solar System Research
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. Gunasingha, 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
M. I. Panasyuk, Lomonosov Moscow State University
A. D. Panov, Lomonosov Moscow State University
W. K.H. Schmidt, Max Plank Institute for Solar System Research
E. S. Seo, University of Maryland, College Park
N. V. Sokolskaya, Lomonosov Moscow State University
J. Wu, University of Maryland, College Park
V. I. Zatsepin, Lomonosov Moscow State University

Abstract

The Advanced Thin Ionization Calorimeter (ATIC) experiment measures the energy spectra of individual elements, from H to Fe, in the energy region from about 100 GeV to tens of TeV. ATIC was flown twice on long-duration balloon flights around the South Pole, 12/00-1/01 (ATIC-1), and 12/02-1/03 (ATIC-2). En-ergy deposit spectra for H and He from both flights are presented. The data from ATIC-2 (18 days) show superior resolution and preliminary analysis indicates evolving energy spectra (i.e. becoming harder with increasing energy) consistent with changes expected from propagation models. The data also suggest a slightly steeper source spectrum for H than for He.