Systematics in the Electron Spectrum Measured by ATIC

An analysis of different parameters to separate electrons from protons in the ATIC ex- periment has been performed. Five separate dis- criminants were studied by different Monte Carlo programs, leading to a variety of results. Application to the ATIC data indicates the range of variation possible in the interpretation of the data. The results of this analysis, when compared with the published results (5), show good agreement in the most inter- esting region of energy (from 90 GeV to 600 GeV). The measured electron spectrum is compared with the recent data reported by Fermi/LAT, and there is no major disagreement between ATIC's results and Fermi/LAT. Finally, possible systematics-free, short energy scale features of the ATIC electron spectrum are mentioned. with the ATIC spectrometer by this method was pub- lished in the paper (5). The most notable detail of the electron spectrum reported was an 'excess' of electrons between energies of 300-800 GeV. The main purpose of this report is to investigate possible alternate tech- niques to separate electrons from hadrons based solely upon currently available simulation methodologies. This analysis was carried out completely independent of the previous analysis, starting from the low level procedures of the calibration of the ATIC apparatus (except the calibration of the silicon matrix detector) and analyzing the data with the new discriminants to look at the resulting electron spectrum. Note that all the lines of reasoning and final conclusions of the present work do not comply exactly with techniques of the papers (4), (5) but rather presents an approach, and its implications, for further discussion. We should note also that the results of the present work are preliminary since the work is still in progress.