Abstract
We carried out a long duration balloon flight for observing cosmic-ray electrons above 100 GeV by the Polar Patrol Balloon (PPB) in Antarctica. The observation was continued for 13 days at an average altitude of 35km in January 2004. The detector is an imaging calorimeter composed of ten-thousand scintillating fibers and nine plastic scintillators inserted between lead plates. The performance of the detector was confirmed by beam tests at the CERN-SPS and also investigated by Monte-Carlo simulations. We have collected about 5, 700 events above 100 GeV, including 84 electron candidates. We present a preliminary result of the electron energy spectrum in 100-1, 000 GeV.
